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If the internal angles of $\triangle ABC$ satisfy $\sin A + 2\sin B = 3\sin C$, then the minimum value of $\cos C$ is
\frac{2 \sqrt{10} - 2}{9}
0
7,802.0625
-1
7,802.0625
Triangle $ABC$ with vertices $A(-2, 0)$, $B(1, 4)$ and $C(-3, 2)$ is reflected over the $y$-axis to form triangle $A'B'C'$. What is the length of a segment drawn from $C$ to $C'$?
6
1
1,251.6875
1,251.6875
-1
Dad is $a$ years old this year, which is 4 times plus 3 years more than Xiao Hong's age this year. Xiao Hong's age expressed in an algebraic expression is ____. If Xiao Hong is 7 years old this year, then Dad's age is ____ years old.
31
0.9375
392.125
392.133333
392
Let $m \ge 3$ be an integer and let $S = \{3,4,5,\ldots,m\}$. Find the smallest value of $m$ such that for every partition of $S$ into two subsets, at least one of the subsets contains integers $a$, $b$, and $c$ (not necessarily distinct) such that $ab = c$.
243
0
8,022.375
-1
8,022.375
How many positive integers less than 100 are both a square and a cube?
2
1
1,909.5
1,909.5
-1
What is the product of all real numbers that are tripled when added to their reciprocals?
-\frac{1}{2}
0.875
2,257.5
2,238
2,394
For each positive integer $n$, let $s(n)$ be the sum of the squares of the digits of $n$. For example, $s(15)=1^2+5^2=26$. Determine all integers $n\geq 1$ such that $s(n)=n$.
1
Given the problem, we want to determine all integers \( n \geq 1 \) such that the sum of the squares of the digits of \( n \), denoted as \( s(n) \), is equal to \( n \). To begin, let's express \( n \) in terms of its digits. Suppose \( n \) is a \( k \)-digit number given by: \[ n = d_{k-1} \cdot 10^{k-1} + d_{k-2} ...
0.3125
7,872.3125
7,169
8,192
Given a periodic sequence $\left\{x_{n}\right\}$ that satisfies $x_{n}=\left|x_{n-1}-x_{n-2}\right|(n \geqslant 3)$, if $x_{1}=1$ and $x_{2}=a \geqslant 0$, calculate the sum of the first 2002 terms when the period of the sequence is minimized.
1335
0.5625
7,197.4375
6,423.888889
8,192
Find the minimum value of \[ \sqrt{x^2 + (2 - x)^2} + \sqrt{(2 - x)^2 + (2 + x)^2} \] over all real numbers $x$.
2\sqrt{5}
0.8125
6,609.25
6,244
8,192
\[ \frac{\left(\left(4.625 - \frac{13}{18} \cdot \frac{9}{26}\right) : \frac{9}{4} + 2.5 : 1.25 : 6.75\right) : 1 \frac{53}{68}}{\left(\frac{1}{2} - 0.375\right) : 0.125 + \left(\frac{5}{6} - \frac{7}{12}\right) : (0.358 - 1.4796 : 13.7)} \]
\frac{17}{27}
0.3125
7,092.6875
5,969.8
7,603.090909
A fair coin is tossed 3 times. What is the probability of at least two consecutive heads?
\frac{1}{2}
1. **Total Outcomes**: A fair coin tossed 3 times can result in $2^3 = 8$ possible outcomes. These outcomes are: HHH, HHT, HTH, HTT, THH, THT, TTH, TTT. 2. **Unfavorable Outcomes**: We need to find the outcomes where there are no two consecutive heads. These are: - TTT: No heads at all. - THT: Heads are separate...
0
4,827.625
-1
4,827.625
Roll two dice consecutively. Let the number on the first die be $m$, and the number on the second die be $n$. Calculate the probability that: (1) $m+n=7$; (2) $m=n$; (3) The point $P(m,n)$ is inside the circle $x^2+y^2=16$.
\frac{2}{9}
1
3,350.875
3,350.875
-1
There are 2020 quadratic equations written on the board: $$ \begin{gathered} 2020 x^{2}+b x+2021=0 \\ 2019 x^{2}+b x+2020=0 \\ 2018 x^{2}+b x+2019=0 \\ \ldots \\ x^{2}+b x+2=0 \end{gathered} $$ (each subsequent equation is obtained from the previous one by decreasing the leading coefficient and the constant term by o...
2021
0.875
4,228.3125
3,662.071429
8,192
A certain school is actively preparing for the "Sunshine Sports" activity and has decided to purchase a batch of basketballs and soccer balls totaling $30$ items. At a sports equipment store, each basketball costs $80$ yuan, and each soccer ball costs $60$ yuan. During the purchase period at the school, there is a prom...
2080
1
2,005.625
2,005.625
-1
Given a point P(3, 2) outside the circle $x^2+y^2-2x-2y+1=0$, find the cosine of the angle between the two tangents drawn from this point to the circle.
\frac{3}{5}
0.25
7,261.5
6,007
7,679.666667
There are five students, A, B, C, D, and E, arranged to participate in the volunteer services for the Shanghai World Expo. Each student is assigned one of four jobs: translator, guide, etiquette, or driver. Each job must be filled by at least one person. Students A and B cannot drive but can do the other three jobs, wh...
108
0
8,122.375
-1
8,122.375
Given non-negative numbers $x$, $y$, and $z$ such that $x+y+z=2$, determine the minimum value of $\frac{1}{3}x^3+y^2+z$.
\frac{13}{12}
0.8125
5,962.6875
5,448.230769
8,192
In a sequence of coin tosses, one can keep a record of instances in which a tail is immediately followed by a head, a head is immediately followed by a head, and etc. We denote these by TH, HH, and etc. For example, in the sequence TTTHHTHTTTHHTTH of 15 coin tosses we observe that there are two HH, three HT, four TH, a...
560
0
8,131.875
-1
8,131.875
Simplify the expression: $\left(\cos \frac{2 \pi}{3}+i \sin \frac{2 \pi}{3}\right)^{6} + \left(\cos \frac{4 \pi}{3}+i \sin \frac{4 \pi}{3}\right)^{6}$ using DeMoivre's Theorem.
2
We apply DeMoivre's Theorem to simplify the first expression to $\left(\cos 6 \cdot \frac{2 \pi}{3}+\sin 6 \cdot \frac{2 \pi}{3}\right)=(\cos 4 \pi+\sin 4 \pi)=1+0=1$. Similarly, we simplify the second expression to $\left(\cos 6 \cdot \frac{4 \pi}{3}+\sin 6 \cdot \frac{4 \pi}{3}\right)=(\cos 8 \pi+\sin 8 \pi)=1+0=1$. ...
0.8125
4,116.625
3,176.153846
8,192
Solve the system of equations: \begin{cases} \frac{m}{3} + \frac{n}{2} = 1 \\ m - 2n = 2 \end{cases}
\frac{2}{7}
0.5
2,598.25
2,810.625
2,385.875
Let $p,$ $q,$ $r$ be positive real numbers. Find the smallest possible value of \[4p^3 + 6q^3 + 24r^3 + \frac{8}{3pqr}.\]
16
0
8,192
-1
8,192
Memories all must have at least one out of five different possible colors, two of which are red and green. Furthermore, they each can have at most two distinct colors. If all possible colorings are equally likely, what is the probability that a memory is at least partly green given that it has no red? [i]Proposed by M...
2/5
0.75
4,735.125
4,195.666667
6,353.5
Tori's mathematics test had 75 problems: 10 arithmetic, 30 algebra, and 35 geometry problems. Although she answered $70\%$ of the arithmetic, $40\%$ of the algebra, and $60\%$ of the geometry problems correctly, she did not pass the test because she got less than $60\%$ of the problems right. How many more questions wo...
5
1
2,199.8125
2,199.8125
-1
The line $y = b-x$ with $0 < b < 4$ intersects the $y$-axis at $P$ and the line $x=4$ at $S$. If the ratio of the area of triangle $QRS$ to the area of triangle $QOP$ is 9:25, what is the value of $b$? Express the answer as a decimal to the nearest tenth. [asy] draw((0,-3)--(0,5.5),Arrows); draw((4,-3.5)--(4,5),Arrows...
2.5
0.9375
3,750.5
3,802.466667
2,971
Find the greatest constant $\lambda$ such that for any doubly stochastic matrix of order 100, we can pick $150$ entries such that if the other $9850$ entries were replaced by $0$, the sum of entries in each row and each column is at least $\lambda$. Note: A doubly stochastic matrix of order $n$ is a $n\times n$ matrix...
\frac{17}{1900}
We are given a doubly stochastic matrix of order 100 and need to find the greatest constant \(\lambda\) such that we can select 150 entries in the matrix, and if the other 9850 entries are replaced by 0, the sum of entries in each row and each column is at least \(\lambda\). To solve this, we construct a bipartite gr...
0
8,183.5
-1
8,183.5
Real numbers $x$ and $y$ satisfy the equation $x^2 + y^2 = 10x - 6y - 34$. What is $x+y$?
2
1
2,129.6875
2,129.6875
-1
Given a connected simple graph \( G \) with a known number of edges \( e \), where each vertex has some number of pieces placed on it (each piece can only be placed on one vertex of \( G \)). The only operation allowed is when a vertex \( v \) has a number of pieces not less than the number of its adjacent vertices \( ...
e
0.0625
8,192
8,192
8,192
An ice cream shop offers 6 kinds of ice cream. What is the greatest number of two scoop sundaes that can be made such that each sundae contains two types of ice cream and no two sundaes are the same combination?
15
1
1,415.8125
1,415.8125
-1
Consider a dark rectangle created by merging two adjacent unit squares in an array of unit squares; part as shown below. If the first ring of squares around this center rectangle contains 10 unit squares, how many unit squares would be in the $100^{th}$ ring?
802
0.8125
5,293.3125
5,021.846154
6,469.666667
A man buys a house for $15,000 and wants to achieve a $6\%$ return on his investment while incurring a yearly tax of $450$, along with an additional $200$ yearly for owner's insurance. The percentage he sets aside from monthly rent for maintenance remains $12\frac{1}{2}\%$. Calculate the monthly rent.
147.62
0.5
6,552
5,640.875
7,463.125
What is the value of $(3x + 2y) - (3x - 2y)$ when $x = -2$ and $y = -1$?
-4
The expression $(3x + 2y) - (3x - 2y)$ is equal to $3x + 2y - 3x + 2y$ which equals $4y$. When $x = -2$ and $y = -1$, this equals $4(-1)$ or $-4$.
1
2,037.3125
2,037.3125
-1
Determine the real value of $t$ that minimizes the expression \[ \sqrt{t^2 + (t^2 - 1)^2} + \sqrt{(t-14)^2 + (t^2 - 46)^2}. \]
7/2
0
8,192
-1
8,192
If 18 bahs are equal to 30 rahs, and 6 rahs are equivalent to 10 yahs, how many bahs are equal to 1200 yahs?
432
0.5625
5,769.0625
3,884.555556
8,192
Given that $a$ is an odd multiple of $7767$, find the greatest common divisor of $6a^2+49a+108$ and $2a+9$.
9
1
4,925.9375
4,925.9375
-1
Calculate the value of the expression \(\sin \frac{b \pi}{36}\), where \(b\) is the sum of all distinct numbers obtained from the number \(a = 987654321\) by cyclic permutations of its digits (in a cyclic permutation, all the digits of the number, except the last one, are shifted one place to the right, and the last di...
\frac{\sqrt{2}}{2}
0
6,512.0625
-1
6,512.0625
In the parallelogram \(ABCD\), the longer side \(AD\) is 5. The angle bisectors of angles \(A\) and \(B\) intersect at point \(M\). Find the area of the parallelogram, given that \(BM = 2\) and \(\cos \angle BAM = \frac{4}{5}\).
16
0.125
7,793
7,204.5
7,877.071429
Quadrilateral $ABCD$ has right angles at $B$ and $C$, $\triangle ABC \sim \triangle BCD$, and $AB < BC$. There is a point $E$ on line segment $CD$ such that $\triangle ABC \sim \triangle CED$ and the area of $\triangle AED$ is $9$ times the area of $\triangle CED$. What is $\tfrac{BC}{AB}$?
10.25
0
8,192
-1
8,192
What is the value of \(a + b + c + d\) if $$ \begin{gathered} 6a + 2b = 3848 \\ 6c + 3d = 4410 \\ a + 3b + 2d = 3080 \end{gathered} $$
1986
0.9375
3,989.3125
4,039.066667
3,243
There is a moving point \( M \) on the base \( A_{1}B_{1}C_{1}D_{1} \) of the cube \( ABCD - A_{1}B_{1}C_{1}D_{1} \), and \( BM \parallel \) plane \( ADC \). Find the maximum value of \( \tan \angle D_{1}MD \).
\sqrt{2}
0
8,192
-1
8,192
Four identical point charges are initially placed at the corners of a square, storing a total energy of 20 Joules. Determine the total amount of energy stored if one of these charges is moved to the center of the square.
10\sqrt{2} + 10
0
7,830
-1
7,830
When a certain unfair die is rolled, an even number is $5$ times as likely to appear as an odd number. The die is rolled twice. Calculate the probability that the sum of the numbers rolled is odd.
\frac{5}{18}
0.8125
4,276.5625
3,853.153846
6,111.333333
Find the sum of the positive divisors of 18.
39
1
1,968.1875
1,968.1875
-1
The polynomial $-5x^2-xy^4+2^6xy+3$ has     terms, and the degree of this polynomial is     . The coefficient of the highest degree term is     .
-1
0.9375
1,392.75
1,443.066667
638
In triangle $A B C$, let the parabola with focus $A$ and directrix $B C$ intersect sides $A B$ and $A C$ at $A_{1}$ and $A_{2}$, respectively. Similarly, let the parabola with focus $B$ and directrix $C A$ intersect sides $B C$ and $B A$ at $B_{1}$ and $B_{2}$, respectively. Finally, let the parabola with focus $C$ and...
\frac{6728}{3375}
By the definition of a parabola, we get $A A_{1}=A_{1} B \sin B$ and similarly for the other points. So $\frac{A B_{2}}{A B}=\frac{A C_{1}}{A C}$, giving $B_{2} C_{1} \| B C$, and similarly for the other sides. So $D E F$ (WLOG, in that order) is similar to $A B C$. It suffices to scale after finding the length of $E F...
0
8,192
-1
8,192
A projectile is launched with an initial velocity of $u$ at an angle of $\phi$ from the horizontal. The trajectory of the projectile is given by the parametric equations: \[ x = ut \cos \phi, \] \[ y = ut \sin \phi - \frac{1}{2} gt^2, \] where $t$ is time and $g$ is the acceleration due to gravity. Suppose $u$ is const...
\frac{\pi}{8}
0.375
7,475.0625
6,280.166667
8,192
In $\triangle ABC$, $AC:CB = 3:4$. The external angle bisector of $\angle C$ intersects the extension of $BA$ at $P$ (with $A$ between $P$ and $B$). Find the ratio $PA:AB$.
3:1
0.8125
4,787.0625
4,433.538462
6,319
A portion of the graph of $y = G(x)$ is shown in red below. The distance between grid lines is $1$ unit. Compute $G(G(G(G(G(1)))))$. [asy] size(150); real ticklen=3; real tickspace=2; real ticklength=0.1cm; real axisarrowsize=0.14cm; pen axispen=black+1.3bp; real vectorarrowsize=0.2cm; real tickdown=-0.5; real tick...
5
1
2,459.5
2,459.5
-1
If $P(x)$ denotes a polynomial of degree $n$ such that $P(k)=\frac{k}{k+1}$ for $k=0,1,2,\ldots,n$, determine $P(n+1)$.
$\frac{n+1}{n+2}$
We are given that $P(x)$ is a polynomial of degree $n$ such that $P(k) = \frac{k}{k+1}$ for $k = 0, 1, 2, \ldots, n$. We need to find $P(n+1)$. 1. **Using Lagrange Interpolation Formula:** The Lagrange Interpolation Formula for a polynomial $P(x)$ that takes values $P(k) = y_k$ at points $x_k$ for $k = 0, 1, 2, \ld...
0
6,951.5625
-1
6,951.5625
In a certain entertainment unit, each member can sing or dance at least one of the two. It is known that there are 4 people who can sing and 5 people who can dance. Now, 2 people are selected from them to participate in a social charity performance. Let $\xi$ be the number of people selected who can both sing and dance...
\frac{4}{7}
0.75
5,349.4375
4,401.916667
8,192
Given a three-digit natural number \(abc\) with digits \(a\), \(b\), and \(c\) in the hundreds, tens, and units places respectively, and where \(a > b\) and \(c > b\), with \(a, b, c \in \{0, 2, 3, 4, 5\}\) and \(a, b, c\) distinct, calculate the number of concave numbers.
20
0.5625
6,960.9375
6,003.444444
8,192
The fraction $\frac{\sqrt{a^2+x^2}-\frac{x^2-a^2}{\sqrt{a^2+x^2}}}{a^2+x^2}$ reduces to:
\frac{2a^2}{(a^2+x^2)^{\frac{3}{2}}}
1. **Simplify the Numerator**: Start by simplifying the numerator of the given fraction: \[ \sqrt{a^2+x^2} - \frac{x^2-a^2}{\sqrt{a^2+x^2}} \] Multiply the second term by $\frac{\sqrt{a^2+x^2}}{\sqrt{a^2+x^2}}$ to get a common denominator: \[ \sqrt{a^2+x^2} - \frac{x^2-a^2}{\sqrt{a^2+x^2}} \cdot \frac...
0
3,841.75
-1
3,841.75
The value of $x$ is one-half the value of $y$, and the value of $y$ is one-fifth the value of $z$. If $z$ is 60, what is the value of $x$?
6
1
770.8125
770.8125
-1
For a given point $P$ on the curve $x^2 - y - \ln x = 0$, what is the minimum distance from point $P$ to the line $y = x - 2$?
\sqrt{2}
0.8125
6,485.3125
6,091.461538
8,192
Gavrila is in an elevator cabin which is moving downward with a deceleration of 5 m/s². Find the force with which Gavrila presses on the floor. Gavrila's mass is 70 kg, and the acceleration due to gravity is 10 m/s². Give the answer in newtons, rounding to the nearest whole number if necessary.
350
0.375
3,474.3125
2,989.5
3,765.2
There are 3 complex numbers $a+bi$, $c+di$, and $e+fi$. If $b=1$, $e=-a-c$, and the sum of the numbers is $-i$, find $d+f$.
-2
1
1,249.875
1,249.875
-1
Let $N$ be the number of positive integers that are less than or equal to $2003$ and whose base-$2$ representation has more $1$'s than $0$'s. Find the remainder when $N$ is divided by $1000$.
155
We will count the number of it $< 2^{11}=2048$ instead of $2003$ (In other words, the length of the base-2 representation is at most $11$. If there are even digits, $2n$, then the leftmost digit is $1$, the rest, $2n-1$, has odd number of digits. In order for the base-2 representation to have more $1$'s, we will need m...
0
8,192
-1
8,192
We are allowed to remove exactly one integer from the list $$-1,0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11,$$and then we choose two distinct integers at random from the remaining list. What number should we remove if we wish to maximize the probability that the sum of the two chosen numbers is 10?
5
0.5625
6,499.4375
5,183
8,192
Determine the number of ways to arrange the letters of the word MAMMAAD.
140
0.5
2,532.875
2,607.5
2,458.25
Calculate the value of $V_3$ for the polynomial $f(x) = 2x^6 + 5x^5 + 6x^4 + 23x^3 - 8x^2 + 10x - 3$ at $x = -4$ using the Horner's method.
-49
0.625
3,940.8125
3,407
4,830.5
Solve the equations: (1) 2x^2 - 5x + 1 = 0; (2) 3x(x - 2) = 2(2 - x).
-\frac{2}{3}
0.625
1,989.625
2,041.2
1,903.666667
In $\triangle ABC$, $a, b, c$ are the sides opposite to angles $A, B, C$ respectively, and angles $A, B, C$ form an arithmetic sequence. (1) Find the measure of angle $B$. (2) If $a=4$ and the area of $\triangle ABC$ is $S=5\sqrt{3}$, find the value of $b$.
\sqrt{21}
0.875
4,918.25
4,631.428571
6,926
One focus of the ellipse $\frac{x^2}{2} + y^2 = 1$ is at $F = (1,0).$ There exists a point $P = (p,0),$ where $p > 0,$ such that for any chord $\overline{AB}$ that passes through $F,$ angles $\angle APF$ and $\angle BPF$ are equal. Find $p.$ [asy] unitsize(2 cm); pair A, B, F, P; path ell = xscale(sqrt(2))*Circle((...
2
0.25
7,886.6875
6,970.75
8,192
Let $S$ be a set, $|S|=35$. A set $F$ of mappings from $S$ to itself is called to be satisfying property $P(k)$, if for any $x,y\in S$, there exist $f_1, \cdots, f_k \in F$ (not necessarily different), such that $f_k(f_{k-1}(\cdots (f_1(x))))=f_k(f_{k-1}(\cdots (f_1(y))))$. Find the least positive integer $m$, such tha...
595
Let \( S \) be a set with \( |S| = 35 \). A set \( F \) of mappings from \( S \) to itself is said to satisfy property \( P(k) \) if for any \( x, y \in S \), there exist \( f_1, f_2, \ldots, f_k \in F \) (not necessarily different) such that \( f_k(f_{k-1}(\cdots (f_1(x)) \cdots )) = f_k(f_{k-1}(\cdots (f_1(y)) \cdot...
0
7,511.125
-1
7,511.125
Let $z$ and $w$ be complex numbers such that $|z + 1 + 3i| = 1$ and $|w - 7 - 8i| = 3.$ Find the smallest possible value of $|z - w|.$
\sqrt{185} - 4
0.75
5,843.1875
5,060.25
8,192
$A$ and $B$ move uniformly along two straight paths intersecting at right angles in point $O$. When $A$ is at $O$, $B$ is $500$ yards short of $O$. In two minutes they are equidistant from $O$, and in $8$ minutes more they are again equidistant from $O$. Then the ratio of $A$'s speed to $B$'s speed is:
5/6
Let the speeds of $A$ and $B$ be $v_A$ and $v_B$ respectively, and let the distance from $O$ be measured in yards. Since $A$ and $B$ move along paths that intersect at right angles, we can consider their movements along the x-axis and y-axis respectively. 1. **Initial Conditions:** - When $A$ is at $O$, $B$ is 500 ...
0
7,309.125
-1
7,309.125
Let \(\triangle ABC\) be inscribed in the unit circle \(\odot O\), with the center \(O\) located within \(\triangle ABC\). If the projections of point \(O\) onto the sides \(BC\), \(CA\), and \(AB\) are points \(D\), \(E\), and \(F\) respectively, find the maximum value of \(OD + OE + OF\).
\frac{3}{2}
0.8125
4,629
4,279
6,145.666667
Let $n$ be a 5-digit number, and let $q$ and $r$ be the quotient and the remainder, respectively, when $n$ is divided by $200$. For how many values of $n$ is $q+r$ divisible by $7$?
13050
0
8,126.1875
-1
8,126.1875
A given finite number of lines in the plane, no two of which are parallel and no three of which are concurrent, divide the plane into finite and infinite regions. In each finite region we write $1$ or $-1$. In one operation, we can choose any triangle made of three of the lines (which may be cut by other lines in the c...
\text{No}
Consider a finite number of lines in the plane, none of which are parallel, and no three of which are concurrent. These lines divide the plane into several regions—both finite and infinite. ### Problem Analysis In this scenario, we assign the number \( 1 \) or \( -1 \) to each of the finite regions. The operation al...
0
8,176.4375
-1
8,176.4375
There are 5 people standing in a row, where A and B must stand next to each other, and C and D cannot stand next to each other. How many different arrangements are there?
24
0.1875
7,928.1875
7,357
8,060
Determine the largest natural number \( n \) such that \[ 4^{995} + 4^{1500} + 4^{n} \] is a square number.
2004
0.0625
8,192
8,192
8,192
Find \( k \) such that \((a+b)(b+c)(c+a) = (a+b+c)(ab+bc+ca) + k \cdot abc\).
-1
0.9375
4,524.9375
4,280.466667
8,192
The degree measures of the angles in a convex 18-sided polygon form an increasing arithmetic sequence with integer values. Find the degree measure of the smallest angle.
143
0.9375
3,455.625
3,139.866667
8,192
What is the value of $101^{4} - 4 \cdot 101^{3} + 6 \cdot 101^2 - 4 \cdot 101 + 1$? (No calculators!)
100000000
0.75
3,862.125
2,418.833333
8,192
Let $r(\theta) = \frac{1}{1-\theta}$. What is $r(r(r(r(r(r(30))))))$ (where $r$ is applied $6$ times)?
30
1
4,067.625
4,067.625
-1
Define the sequence of positive integers $\left\{a_{n}\right\}$ as follows. Let $a_{1}=1, a_{2}=3$, and for each $n>2$, let $a_{n}$ be the result of expressing $a_{n-1}$ in base $n-1$, then reading the resulting numeral in base $n$, then adding 2 (in base $n$). For example, $a_{2}=3_{10}=11_{2}$, so $a_{3}=11_{3}+2_{3}...
23097
We claim that for nonnegative integers $m$ and for $0 \leq n<3 \cdot 2^{m}, a_{3 \cdot 2^{m}+n}=\left(3 \cdot 2^{m}+n\right)(m+2)+2 n$. We will prove this by induction; the base case for $a_{3}=6$ (when $m=0$, $n=0$) is given in the problem statement. Now, suppose that this is true for some pair $m$ and $n$. We will di...
0
8,192
-1
8,192
Once upon a time, a team of Knights and a team of Liars met in the park and decided to ride a circular carousel that can hold 40 people (the "Chain" carousel, where everyone sits one behind the other). When they took their seats, each person saw two others: one in front and one behind. Each person then said, "At least ...
26
0
8,110.75
-1
8,110.75
Given that $\left\{a_{n}\right\}$ is an arithmetic sequence with a nonzero common difference and $\left\{b_{n}\right\}$ is a geometric sequence where $a_{1}=3, b_{1}=1, a_{2}=b_{2}, 3a_{5}=b_{3}$, and there exist constants $\alpha$ and $\beta$ such that for every positive integer $n$, $a_{n} = \log_{\alpha} b_{n} + \be...
\sqrt[3]{3} + 3
0
4,009.5625
-1
4,009.5625
Find all integers $m$ and $n$ such that the fifth power of $m$ minus the fifth power of $n$ is equal to $16mn$.
(m, n) = (0, 0) \text{ and } (m, n) = (-2, 2)
We are tasked with finding all integer pairs \((m, n)\) such that: \[ m^5 - n^5 = 16mn \] **Step 1: Algebraic Manipulation** We begin by rewriting the given equation as: \[ m^5 - n^5 - 16mn = 0 \] **Step 2: Factorization** Using the identity for the difference of powers, we have: \[ m^5 - n^5 = (m - n)(m^4 + m^...
0
8,192
-1
8,192
Two adjacent faces of a tetrahedron, representing equilateral triangles with side length 3, form a dihedral angle of 30 degrees. The tetrahedron rotates around the common edge of these faces. Find the maximum area of the projection of the rotating tetrahedron onto a plane containing this edge.
\frac{9\sqrt{3}}{4}
0
8,192
-1
8,192
Find the number of ordered pairs $(a,b)$ of complex numbers such that \[a^4 b^6 = a^8 b^3 = 1.\]
24
0
7,954.3125
-1
7,954.3125
The orthocenter of triangle $DEF$ divides altitude $\overline{DM}$ into segments with lengths $HM = 10$ and $HD = 24.$ Calculate $\tan E \tan F.$
3.4
0
7,717.875
-1
7,717.875
An influenza outbreak occurred in three areas, $A$, $B$, and $C$, where $6\%$, $5\%$, and $4\%$ of the population in each area have the flu, respectively. Assuming the population ratios in these three areas are $6:5:4$, if a person is randomly selected from these three areas, the probability that this person has the fl...
\frac{77}{1500}
0.75
5,753.25
4,940.333333
8,192
The equation $y = -6t^2 - 10t + 56$ describes the height (in feet) of a ball thrown downward at 10 feet per second from a height of 56 feet from the surface from Mars. In how many seconds will the ball hit the ground? Express your answer as a decimal rounded to the nearest hundredth.
2.33
1
3,451.9375
3,451.9375
-1
Find the volume of the region in space defined by \[|x - y + z| + |x - y - z| \le 10\]and $x, y, z \ge 0$.
62.5
0
8,192
-1
8,192
Given that $\overrightarrow{a}$ and $\overrightarrow{b}$ are non-zero vectors and $(\overrightarrow{a} - 6\overrightarrow{b}) \perp \overrightarrow{a}$, $(2\overrightarrow{a} - 3\overrightarrow{b}) \perp \overrightarrow{b}$, find the angle between $\overrightarrow{a}$ and $\overrightarrow{b}$.
\frac{\pi}{3}
0.0625
3,130.625
3,180
3,127.333333
What is the area of the region enclosed by the graph of the equation $x^2+y^2=|x|+|y|?$
\pi + 2
1. **Analyze the given equation:** The equation provided is $x^2 + y^2 = |x| + |y|$. This equation is symmetric with respect to both the x-axis and y-axis due to the absolute value terms. 2. **Consider the first quadrant ($x \geq 0$, $y \geq 0$):** In this quadrant, $|x| = x$ and $|y| = y$. Thus, the equation simplifi...
0
8,192
-1
8,192
Forty teams play a tournament in which every team plays every other team exactly once. No ties occur, and each team has a $50 \%$ chance of winning any game it plays. The probability that no two teams win the same number of games is $\frac mn,$ where $m_{}$ and $n_{}$ are relatively prime positive integers. Find $\log_...
742
There are ${40 \choose 2} = 780$ total pairings of teams, and thus $2^{780}$ possible outcomes. In order for no two teams to win the same number of games, they must each win a different number of games. Since the minimum and maximum possible number of games won are 0 and 39 respectively, and there are 40 teams in total...
0.5
4,699.0625
4,012
5,386.125
Given that $11^{-1} \equiv 3 \pmod{31}$, find $20^{-1} \pmod{31}$. Provide the result as a residue modulo 31 (a number between 0 and 30, inclusive).
28
0
6,666.9375
-1
6,666.9375
Find the positive real number $x$ such that $\lfloor x \rfloor \cdot x = 70$. Express $x$ as a decimal.
8.75
1
2,274.9375
2,274.9375
-1
Two circles, one with radius 4 and the other with radius 5, are externally tangent to each other and are circumscribed by a third circle. Calculate the area of the shaded region formed between these three circles. Express your answer in terms of $\pi$.
40\pi
0.375
6,581.25
3,949.833333
8,160.1
Suppose \[\frac{1}{x^3-x^2-21x+45}=\frac{A}{x+5}+\frac{B}{x-3} + \frac{C}{(x - 3)^2}\]where $A$, $B$, and $C$ are real constants. What is $A$?
\frac{1}{64}
0.8125
4,121
3,578
6,474
Given the parabola $C$: $y^{2}=4x$ with focus $F$, two lines $l_{1}$ and $l_{2}$ are drawn through point $F$. Line $l_{1}$ intersects the parabola $C$ at points $A$ and $B$, and line $l_{2}$ intersects the parabola $C$ at points $D$ and $E$. If the sum of the squares of the slopes of $l_{1}$ and $l_{2}$ is $1$, then fi...
24
0.5625
7,252.4375
6,634.444444
8,047
Dave arrives at an airport which has twelve gates arranged in a straight line with exactly $100$ feet between adjacent gates. His departure gate is assigned at random. After waiting at that gate, Dave is told the departure gate has been changed to a different gate, again at random. Let the probability that Dave walks $...
52
There are $12 \cdot 11 = 132$ possible situations ($12$ choices for the initially assigned gate, and $11$ choices for which gate Dave's flight was changed to). We are to count the situations in which the two gates are at most $400$ feet apart. If we number the gates $1$ through $12$, then gates $1$ and $12$ have four ...
0.25
6,512.25
5,886.5
6,720.833333
Given that the vertex of angle $\theta$ is at the origin of the coordinate, its initial side coincides with the positive half of the $x$-axis, and its terminal side lies on the ray $y=\frac{1}{2}x (x\leqslant 0)$. (I) Find the value of $\cos(\frac{\pi}{2}+\theta)$; (II) If $\cos(\alpha+\frac{\pi}{4})=\sin\theta$, fin...
-\frac{\sqrt{2}}{10}
0
6,553.1875
-1
6,553.1875
Let \( \triangle DEF \) be a triangle and \( H \) the foot of the altitude from \( D \) to \( EF \). If \( DE = 60 \), \( DF = 35 \), and \( DH = 21 \), what is the difference between the minimum and the maximum possible values for the area of \( \triangle DEF \)?
588
0.4375
7,503.8125
6,619
8,192
Let \( S \) be the set of points whose coordinates \( x \), \( y \), and \( z \) are integers that satisfy \( 0 \leq x \leq 2 \), \( 0 \leq y \leq 3 \), and \( 0 \leq z \leq 4 \). Two distinct points are randomly chosen from \( S \). Find the probability that the midpoint of the two chosen points also belongs to \( S \...
23/177
0.125
8,086.375
7,638.5
8,150.357143
Square \(ABCD\) has points \(A\) and \(B\) on the \(x\)-axis, and points \(C\) and \(D\) below the \(x\)-axis on the parabola with equation \(y = x^{2} - 4\). What is the area of \(ABCD\)?
24 - 8\sqrt{5}
0.1875
8,106.375
7,735.333333
8,192
Given the function $f(x)=\sin(2x+ \frac{\pi}{6})+\sin(2x- \frac{\pi}{6})+\cos 2x+a$ ($a\in\mathbb{R}$, $a$ is a constant), (1) Find the smallest positive period of the function; (2) Find the intervals of monotonic increase of the function; (3) If $x\in\left[0, \frac{\pi}{2}\right]$ and the minimum value of $f(x)$ is...
-1
0.75
5,942.3125
5,452.5
7,411.75
Given that the four vertices A, B, C, D of the tetrahedron A-BCD are all on the surface of the sphere O, AC ⊥ the plane BCD, and AC = 2√2, BC = CD = 2, calculate the surface area of the sphere O.
16\pi
0.5
6,913
5,634
8,192
There are 99 children standing in a circle, each initially holding a ball. Every minute, each child with a ball throws their ball to one of their two neighbors. If a child receives two balls, one of the balls is irrevocably lost. What is the minimum amount of time after which only one ball can remain with the children?
98
0.3125
7,698.0625
6,611.4
8,192