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31,300
Let $S=\{1,2,\ldots ,98\}$ . Find the least natural number $n$ such that we can pick out $10$ numbers in any $n$ -element subset of $S$ satisfying the following condition: no matter how we equally divide the $10$ numbers into two groups, there exists a number in one group such that it is coprime to the other ...
50
22.65625
31,301
A council consists of nine women and three men. During their meetings, they sit around a round table with the women in indistinguishable rocking chairs and the men on indistinguishable stools. How many distinct ways can the nine chairs and three stools be arranged around the round table for a meeting?
55
23.4375
31,302
What is the smallest positive integer that is neither prime nor a cube and that has an even number of prime factors, all greater than 60?
3721
17.96875
31,303
For what values of the parameter \( a \in \mathbb{R} \) does the maximum distance between the roots of the equation \[ a \tan^{3} x + \left(2-a-a^{2}\right) \tan^{2} x + \left(a^{2}-2a-2\right) \tan x + 2a = 0 \] belonging to the interval \(\left(-\frac{\pi}{2} , \frac{\pi}{2}\right)\), take the smallest value? Find...
\frac{\pi}{4}
3.90625
31,304
Given that $\overrightarrow{a}$ and $\overrightarrow{b}$ are non-zero vectors, $\overrightarrow{m} = \overrightarrow{a} + t \overrightarrow{b} (t \in \mathbb{R})$, $|\overrightarrow{a}| = 1$, $|\overrightarrow{b}| = 2$, the minimum value of $|\overrightarrow{m}|$ is obtained only when $t = \frac{1}{4}$. Determine the a...
\frac{2\pi}{3}
98.4375
31,305
Compute the largest integer \( k \) such that \( 2010^k \) divides \( 2010! \).
30
97.65625
31,306
Given that point P is on the curve $y=\frac{1}{2}{{e}^{x}}$ and point Q is on the curve $y=x$, determine the minimum value of the distance $|PQ|$.
\frac{\sqrt{2}}{2}(1 - \ln 2)
0.78125
31,307
Cara is in a group photo with her seven friends. If Cara must stand between two of her friends, how many different possible pairs of friends could she be standing between?
21
83.59375
31,308
Given that all four roots of the equation $2x^4 + mx^2 + 8 = 0$ are integers, then $m = \ $, and the polynomial $2x^4 + mx^2 + 8$ can be factored into $\ $.
-10
1.5625
31,309
Given the function $f(x)=-3x^2+6x$, let ${S_n}$ be the sum of the first $n$ terms of the sequence ${{a_n}}$. The points $(n, {S_n})$ (where $n \in \mathbb{N}^*$) lie on the curve $y=f(x)$. (I) Find the general formula for the terms of the sequence ${{a_n}}$. (II) If ${b_n}={(\frac{1}{2})^{n-1}}$ and ${c_n}=\frac{{a_n...
\frac{1}{2}
38.28125
31,310
There were five teams entered in a competition. Each team consisted of either only boys or only girls. The number of team members was $9, 15, 17, 19$, and $21$. After one team of girls had been knocked out of the competition, the number of girls still competing was three times the number of boys. How many girls were in...
21
21.09375
31,311
Given the parabola $y^{2}=4x$, a line with a slope of $\frac{\pi}{4}$ intersects the parabola at points $P$ and $Q$, and $O$ is the origin of the coordinate system. Find the area of triangle $POQ$.
2\sqrt{2}
0
31,312
In a rectangle of size $3 \times 4$, 4 points are chosen. Find the smallest number $C$ such that the distance between some two of these points does not exceed $C$.
2.5
53.125
31,313
For how many integer values of $m$ , (i) $1\le m \le 5000$ (ii) $[\sqrt{m}] =[\sqrt{m+125}]$ Note: $[x]$ is the greatest integer function
72
1.5625
31,314
Calculate the following expression: \[\left( 1 - \frac{1}{\cos 30^\circ} \right) \left( 1 + \frac{1}{\sin 60^\circ} \right) \left( 1 - \frac{1}{\sin 30^\circ} \right) \left( 1 + \frac{1}{\cos 60^\circ} \right).\]
-1
0.78125
31,315
Given the function $f(x) = \sin(\omega x + \frac{\pi}{6}) (\omega > 0)$, where the graph is symmetric about the point $(x_0, 0)$ and the distance between two adjacent symmetry axes of the function's graph is $\frac{\pi}{2}$, determine the value of $x_0$.
\frac{5\pi}{12}
7.8125
31,316
A bear is in the center of the left down corner of a $100*100$ square .we call a cycle in this grid a bear cycle if it visits each square exactly ones and gets back to the place it started.Removing a row or column with compose the bear cycle into number of pathes.Find the minimum $k$ so that in any bear cycle we ca...
5000
19.53125
31,317
A spinner is divided into six congruent sectors, numbered from 1 to 6. Jane and her brother each spin the spinner once. If the non-negative difference of their numbers is less than 4, Jane wins. Otherwise, her brother wins. What is the probability that Jane wins?
\frac{5}{6}
64.0625
31,318
Eight teams participated in a football tournament, and each team played exactly once against each other team. If a match was drawn then both teams received 1 point; if not then the winner of the match was awarded 3 points and the loser received no points. At the end of the tournament the total number of points gained b...
17
20.3125
31,319
Given that $F\_1$ and $F\_2$ are the left and right foci of the ellipse $(E)$: $\frac{{x}^{2}}{{a}^{2}}+\frac{{y}^{2}}{{b}^{2}}=1 (a > b > 0)$, $M$ and $N$ are the endpoints of its minor axis, and the perimeter of the quadrilateral $MF\_1NF\_2$ is $4$, let line $(l)$ pass through $F\_1$ intersecting $(E)$ at points $A$...
\frac{2}{3}
7.03125
31,320
Given that $x$ is a multiple of $54896$, find the greatest common divisor of $f(x)=(5x+4)(9x+7)(11x+3)(x+12)$ and $x$.
112
11.71875
31,321
Calculate the circulation of the vector field: a) $\vec{A}=x^{2} y^{2} \vec{i}+\vec{j}+z \vec{k}$ along the circle $x^{2}+y^{2}=a^{2}, z=0$; b) $\dot{A}=(x-2 z) \dot{i}+(x+3 y+z) \dot{j}+(5 x+y) \vec{k}$ along the perimeter of the triangle $A B C$ with vertices $A(1,0,0), B(0,1,0), C(0,0,1)$.
-3
59.375
31,322
Given an arc length of 50cm and the central angle corresponding to the arc is 200°, (1) find the radius of the circle containing this arc, (2) find the area of the sector formed by this arc and the radius.
\frac{1125}{\pi}
55.46875
31,323
In our province, the new college entrance examination adopts a "choose 3 out of 7" model, which means choosing 3 subjects from politics, history, geography, physics, chemistry, biology, and technology as elective subjects. How many possible combinations of elective subjects are there? If person A must choose physics an...
92
0
31,324
A regular decagon is formed by connecting three sequentially adjacent vertices of the decagon. Find the probability that all three sides of the triangle are also sides of the decagon.
\frac{1}{12}
62.5
31,325
Given the function $f(x)=\cos (2x- \frac {π}{6})\sin 2x- \frac{1}{4}(x∈R)$ (1) Find the smallest positive period and the monotonically decreasing interval of the function $f(x)$; (2) Find the maximum and minimum values of the function $f(x)$ on $\[- \frac {π}{4},0\]$.
-\frac {1}{2}
67.96875
31,326
In the Cartesian coordinate system, given points A(1, -3), B(4, -1), P(a, 0), and N(a+1, 0), if the perimeter of the quadrilateral PABN is minimal, then find the value of a.
a = \frac{5}{2}
41.40625
31,327
Calculate the value of the expression \( \sqrt{\frac{16^{12} + 8^{15}}{16^5 + 8^{16}}} \).
\frac{3\sqrt{2}}{4}
56.25
31,328
In triangle \(ABC\), the angle at vertex \(B\) is \(\frac{\pi}{3}\), and the line segments connecting the incenter to vertices \(A\) and \(C\) are 4 and 6, respectively. Find the radius of the circle inscribed in triangle \(ABC\).
\frac{6 \sqrt{3}}{\sqrt{19}}
0
31,329
The sequence $\{2n+1\}$ ($n\in\mathbb{N}^*$) is arranged sequentially in brackets such that the first bracket contains one number, the second bracket contains two numbers, the third bracket contains three numbers, the fourth bracket contains four numbers, the fifth bracket contains one number, the sixth bracket contain...
2072
17.1875
31,330
Given that vehicles are not allowed to turn back at a crossroads, calculate the total number of driving routes.
12
3.90625
31,331
Given the hyperbola $C$: $\frac{x^2}{a^2} - y^2 = 1$ $(a > 0)$ and the line $l$: $x + y = 1$, which intersect at two distinct points $A$ and $B$. 1. Find the range of values for $a$. 2. Let $P$ be the intersection point of line $l$ and the $y$-axis, and $\overrightarrow{PA} = \frac{5}{12}\overrightarrow{PB}$. Find the...
\frac{17}{13}
25.78125
31,332
The traditional Chinese mathematical masterpiece "Nine Chapters on the Mathematical Art" records: "There are 5 cows and 2 sheep, worth 19 taels of silver; 2 cows and 5 sheep, worth 16 taels of silver. How much is each cow and each sheep worth in silver?" According to the translation above, answer the following two ques...
7.5
7.8125
31,333
Given a sequence where each term is either 1 or 2, starting with 1, and where between the \(k\)-th 1 and the \((k+1)\)-th 1 there are \(2^{k-1}\) 2's (i.e., the sequence is 1, 2, 1, 2, 2, 1, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, ...), determine the sum of the first 1998 terms of this sequence.
3986
5.46875
31,334
Given the following arrays, each composed of three numbers: $(1,2,3)$, $(2,4,6)$, $(3,8,11)$, $(4,16,20)$, $(5,32,37)$, ..., $(a\_n,b\_n,c\_n)$. If the sum of the first $n$ terms of the sequence $\{c\_n\}$ is denoted as $M\_n$, find the value of $M\_{10}$.
2101
77.34375
31,335
For a four-digit natural number $M$, if the digit in the thousands place is $6$ more than the digit in the units place, and the digit in the hundreds place is $2$ more than the digit in the tens place, then $M$ is called a "naive number." For example, the four-digit number $7311$ is a "naive number" because $7-1=6$ and...
9313
0.78125
31,336
Given an ellipse $\frac {x^{2}}{a^{2}} + \frac {y^{2}}{b^{2}} = 1$ ($a > b > 0$) and a line $l: y = -\frac { \sqrt {3}}{3}x + b$ intersect at two distinct points P and Q. The distance from the origin to line $l$ is $\frac { \sqrt {3}}{2}$, and the eccentricity of the ellipse is $\frac { \sqrt {6}}{3}$. (Ⅰ) Find the eq...
-\frac {7}{6}
0.78125
31,337
Lesha's summer cottage has the shape of a nonagon with three pairs of equal and parallel sides. Lesha knows that the area of the triangle with vertices at the midpoints of the remaining sides of the nonagon is 12 sotkas. Help him find the area of the entire summer cottage.
48
56.25
31,338
Let $ABC$ be a right triangle, right at $B$ , and let $M$ be the midpoint of the side $BC$ . Let $P$ be the point in bisector of the angle $ \angle BAC$ such that $PM$ is perpendicular to $BC (P$ is outside the triangle $ABC$ ). Determine the triangle area $ABC$ if $PM = 1$ and $MC = 5$ .
120
1.5625
31,339
How many different rectangles with sides parallel to the grid can be formed by connecting four of the dots in a $5\times 5$ square array of dots?
100
14.84375
31,340
Given that a person can click four times in sequence and receive one of three types of red packets each time, with the order of appearance corresponding to different prize rankings, calculate the number of different prize rankings that can be obtained if all three types of red packets are collected in any order before ...
18
80.46875
31,341
Given a right triangle where one leg has length $4x + 2$ feet and the other leg has length $(x-3)^2$ feet, find the value of $x$ if the hypotenuse is $5x + 1$ feet.
\sqrt{\frac{3}{2}}
3.90625
31,342
How many different rectangles with sides parallel to the grid can be formed by connecting four of the dots in a $5\times 5$ square array of dots? (Two rectangles are different if they do not share all four vertices.)
100
23.4375
31,343
The function $f: N \to N_0$ is such that $f (2) = 0, f (3)> 0, f (6042) = 2014$ and $f (m + n)- f (m) - f (n) \in\{0,1\}$ for all $m,n \in N$ . Determine $f (2014)$ . $N_0=\{0,1,2,...\}$
671
78.125
31,344
Thirty teams play a tournament where every team plays every other team exactly once. Each game results either in a win or a loss with a $50\%$ chance for either outcome. Calculate the probability that all teams win a unique number of games. Express your answer as $\frac{m}{n}$ where $m$ and $n$ are coprime integers and...
409
20.3125
31,345
In 1980, the per capita income in our country was $255; by 2000, the standard of living had reached a moderately prosperous level, meaning the per capita income had reached $817. What was the annual average growth rate?
6\%
0.78125
31,346
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
31,347
How many distinct trees with exactly 7 vertices are there? Here, a tree in graph theory refers to a connected graph without cycles, which can be simply understood as connecting \(n\) vertices with \(n-1\) edges.
11
15.625
31,348
Let $ABC$ be a triangle with $\angle BAC=117^\circ$ . The angle bisector of $\angle ABC$ intersects side $AC$ at $D$ . Suppose $\triangle ABD\sim\triangle ACB$ . Compute the measure of $\angle ABC$ , in degrees.
42
69.53125
31,349
In a theater performance of King Lear, the locations of Acts II-V are drawn by lot before each act. The auditorium is divided into four sections, and the audience moves to another section with their chairs if their current section is chosen as the next location. Assume that all four sections are large enough to accommo...
1/2
4.6875
31,350
Calculate the following product: $12 \times 0.5 \times 3 \times 0.2 =$ A) $\frac{20}{5}$ B) $\frac{22}{5}$ C) $\frac{16}{5}$ D) $\frac{18}{5}$ E) $\frac{14}{5}$
\frac{18}{5}
93.75
31,351
In a press conference before a championship game, ten players from four teams will be taking questions. The teams are as follows: three Celtics, three Lakers, two Warriors, and two Nuggets. If teammates insist on sitting together and one specific Warrior must sit at the end of the row on the left, how many ways can the...
432
18.75
31,352
Let $a$ and $b$ be real numbers bigger than $1$ . Find maximal value of $c \in \mathbb{R}$ such that $$ \frac{1}{3+\log _{a} b}+\frac{1}{3+\log _{b} a} \geq c $$
\frac{1}{3}
10.15625
31,353
A Gareth sequence is a sequence of numbers where each number after the second is the non-negative difference between the two previous numbers. For example, if a Gareth sequence begins 15, 12, then: - The third number in the sequence is \(15 - 12 = 3\), - The fourth number is \(12 - 3 = 9\), - The fifth number is \(9 -...
64
34.375
31,354
In a regular 15-gon, three distinct segments are chosen at random among the segments whose end-points are the vertices. What is the probability that the lengths of these three segments are the three side lengths of a triangle with positive area? A) $\frac{345}{455}$ B) $\frac{100}{455}$ C) $\frac{310}{455}$ D) $\frac{3...
\frac{345}{455}
27.34375
31,355
Given that a recipe calls for \( 4 \frac{1}{2} \) cups of flour, calculate the amount of flour needed if only half of the recipe is made.
2 \frac{1}{4}
92.1875
31,356
Given that $α$ and $β$ are both acute angles, and $\cos (α+β)=\dfrac{\sin α}{\sin β}$, the maximum value of $\tan α$ is \_\_\_\_.
\dfrac{ \sqrt{2}}{4}
12.5
31,357
In quadrilateral $ABCD$, $\angle A = 120^\circ$, and $\angle B$ and $\angle D$ are right angles. Given $AB = 13$ and $AD = 46$, find the length of $AC$.
62
0
31,358
The equations \[60x^4 + ax^3 + bx^2 + cx + 20 = 0\]and \[20x^5 + dx^4 + ex^3 + fx^2 + gx + 60 = 0\]have a common rational root $r$ which is not an integer, and which is positive. What is $r?$
\frac{1}{2}
75
31,359
What is the fifth-largest divisor of 3,640,350,000?
227,521,875
0
31,360
The mean of one set of seven numbers is 15, and the mean of a separate set of eight numbers is 20. What is the mean of the set of all fifteen numbers?
17.67
42.96875
31,361
Given vectors $\overrightarrow{a}$ and $\overrightarrow{b}$ that satisfy $|\overrightarrow{a}| = 1$, $|\overrightarrow{b}| = \sqrt{3}$, and $(3\overrightarrow{a} - 2\overrightarrow{b}) \perp \overrightarrow{a}$, find the angle between $\overrightarrow{a}$ and $\overrightarrow{b}$.
\frac{\pi}{6}
98.4375
31,362
Given an ellipse $C: \dfrac{x^2}{a^2} + \dfrac{y^2}{b^2} = 1 \left( a > b > 0 \right)$ with eccentricity $\dfrac{\sqrt{3}}{2}$, and the length of its minor axis is $2$. (I) Find the standard equation of the ellipse $C$. (II) Suppose a tangent line $l$ of the circle $O: x^2 + y^2 = 1$ intersects curve $C$ at points $A...
\dfrac{5}{4}
7.03125
31,363
Among the positive integers that can be expressed as the sum of 2005 consecutive integers, which occupies the 2005th position when arranged in order? *Roland Hablutzel, Venezuela* <details><summary>Remark</summary>The original question was: Among the positive integers that can be expressed as the sum of 2004 consec...
2005 * 2004 * 2005
0
31,364
Find all values of \( a \) such that the roots \( x_1, x_2, x_3 \) of the polynomial \[ x^3 - 6x^2 + ax + a \] satisfy \[ \left(x_1 - 3\right)^3 + \left(x_2 - 3\right)^3 + \left(x_3 - 3\right)^3 = 0. \]
-9
35.15625
31,365
There are eight envelopes numbered 1 to 8. Find the number of ways in which 4 identical red buttons and 4 identical blue buttons can be put in the envelopes such that each envelope contains exactly one button, and the sum of the numbers on the envelopes containing the red buttons is more than the sum of the numbers on ...
31
82.8125
31,366
In the diagram below, $ABCD$ is a trapezoid such that $\overline{AB}\parallel \overline{CD}$ and $\overline{AC}\perp\overline{CD}$. If $CD = 15$, $\tan D = 2$, and $\tan B = 2.5$, then what is $BC$?
2\sqrt{261}
0
31,367
A 6x6x6 cube is formed by assembling 216 unit cubes. Two 1x6 stripes are painted on each of the six faces of the cube parallel to the edges, with one stripe along the top edge and one along the bottom edge of each face. How many of the 216 unit cubes have no paint on them?
144
10.15625
31,368
In a cultural performance, there are already 10 programs arranged in the program list. Now, 3 more programs are to be added, with the requirement that the relative order of the originally scheduled 10 programs remains unchanged. How many different arrangements are there for the program list? (Answer with a number).
1716
5.46875
31,369
A line segment starts at $(2, 4)$ and ends at the point $(7, y)$ with $y > 0$. The segment is 6 units long. Find the value of $y$.
4 + \sqrt{11}
65.625
31,370
Let planes \( \alpha \) and \( \beta \) be parallel to each other. Four points are selected on plane \( \alpha \) and five points are selected on plane \( \beta \). What is the maximum number of planes that can be determined by these points?
72
5.46875
31,371
Suppose we want to divide 12 puppies into three groups where one group has 4 puppies, one has 6 puppies, and one has 2 puppies. Determine how many ways we can form the groups such that Coco is in the 4-puppy group and Rocky is in the 6-puppy group.
2520
90.625
31,372
At a school cafeteria, Jenny wants to buy a meal consisting of one main dish, one drink, one dessert, and one side dish. The list below contains Jenny's preferred choices available: \begin{tabular}{ |c|c|c|c| } \hline \textbf{Main Dishes} & \textbf{Drinks} & \textbf{Desserts} & \textbf{Side Dishes} \\ \hline Spaghetti...
48
62.5
31,373
Let \( M(x, y, z) \) represent the minimum of the three numbers \( x, y, z \). If the quadratic function \( f(x) = ax^2 + bx + c \) (where \( a, b, c > 0 \)) has a zero, determine the maximum value of \( M \left( \frac{b+c}{a}, \frac{c+a}{b}, \frac{a+b}{c} \right) \).
\frac{5}{4}
3.125
31,374
Given that the polynomial $x^2 - kx + 24$ has only positive integer roots, find the average of all distinct possibilities for $k$.
15
96.875
31,375
Let the function $f(x)=a\ln x-x- \frac {1}{2}x^{2}$. (I) For $a=2$, find the extreme values of the function $f(x)$. (II) Discuss the monotonicity of the function $f(x)$.
-\frac{3}{2}
40.625
31,376
Given the function $y=\cos(2x+ \frac {\pi}{3})$, determine the horizontal shift required to obtain this function from the graph of $y=\sin 2x$.
\frac{5\pi}{12}
28.90625
31,377
The ratio of the area of the rectangle to the area of the decagon can be calculated given that a regular decagon $ABCDEFGHIJ$ contains a rectangle $AEFJ$.
\frac{2}{5}
4.6875
31,378
The numbers from 1 to 9 are placed in the cells of a 3x3 table so that the sum of the numbers on one diagonal is 7 and the sum on the other diagonal is 21. What is the sum of the numbers in the five shaded cells?
25
47.65625
31,379
A jar contains $2$ yellow candies, $4$ red candies, and $6$ blue candies. Candies are randomly drawn out of the jar one-by-one and eaten. The probability that the $2$ yellow candies will be eaten before any of the red candies are eaten is given by the fraction $\frac{m}{n}$ where $m$ and $n$ are relativel...
16
46.875
31,380
A plane flies between two cities. With the tailwind, it takes 5 hours and 30 minutes, and against the wind, it takes 6 hours. Given that the wind speed is 24 kilometers per hour, and assuming the plane's flying speed is $x$ kilometers per hour, then the speed of the plane with the tailwind is     kilometers per hour, a...
528
61.71875
31,381
Find the maximum real number \( k \) such that for any positive numbers \( a \) and \( b \), the following inequality holds: $$ (a+b)(ab+1)(b+1) \geqslant k \, ab^2. $$
27/4
0.78125
31,382
Given $\cos \alpha= \frac {1}{3}$, $\cos (\alpha+\beta)=- \frac {1}{3}$, and $\alpha$, $\beta\in(0, \frac {\pi}{2})$, find the value of $\cos (\alpha-\beta)$.
\frac{23}{27}
57.8125
31,383
Segments $BD$ and $AE$ intersect at $C$, with $AB = BC$ and $CD = DE = EC$. Additionally, $\angle A = 4 \angle B$. Determine the degree measure of $\angle D$. A) 45 B) 50 C) 52.5 D) 55 E) 60
52.5
8.59375
31,384
A factory conducted a survey on the defective parts produced by a team. The number of defective parts produced by the team each day in 7 days is as follows (unit: pieces): 3, 3, 0, 2, 3, 0, 3. What is the value of the variance of the number of defective parts produced by the team in 7 days?
\frac{12}{7}
31.25
31,385
If there are exactly $3$ integer solutions for the inequality system about $x$: $\left\{\begin{array}{c}6x-5≥m\\ \frac{x}{2}-\frac{x-1}{3}<1\end{array}\right.$, and the solution to the equation about $y$: $\frac{y-2}{3}=\frac{m-2}{3}+1$ is a non-negative number, find the sum of all integers $m$ that satisfy the conditi...
-5
62.5
31,386
Choose any $2$ numbers from $-5$, $-3$, $-1$, $2$, and $4$. Let the maximum product obtained be denoted as $a$, and the minimum quotient obtained be denoted as $b$. Then the value of $\frac{a}{b}$ is ______.
-\frac{15}{4}
5.46875
31,387
Let $f(x)$ have a domain of $R$, $f(x+1)$ be an odd function, and $f(x+2)$ be an even function. When $x\in [1,2]$, $f(x)=ax^{2}+b$. If $f(0)+f(3)=6$, then calculate the value of $f\left(\frac{9}{2}\right)$.
\frac{5}{2}
2.34375
31,388
Three boys and three girls are lined up for a photo. Boy A is next to boy B, and exactly two girls are next to each other. Calculate the total number of different ways they can be arranged.
144
13.28125
31,389
The length of edge PQ of a tetrahedron PQRS measures 51 units, and the lengths of the other edges are 12, 19, 24, 33, and 42 units. Determine the length of edge RS.
24
5.46875
31,390
Given that there are 10 streetlights numbered from 1 to 10, two of which will be turned off under the conditions that two adjacent lights cannot be turned off at the same time and the lights at both ends cannot be turned off either, calculate the number of ways to turn off the lights.
21
81.25
31,391
Let $S$ be the set of natural numbers that cannot be written as the sum of three squares. Legendre's three-square theorem states that $S$ consists of precisely the integers of the form $4^a(8b+7)$ where $a$ and $b$ are nonnegative integers. Find the smallest $n\in\mathbb N$ such that $n$ and $n+1$ are b...
111
0
31,392
Increase Grisha's yield by 40% and Vasya's yield by 20%. Grisha, the most astute among them, calculated that in the first case their total yield would increase by 1 kg; in the second case, it would decrease by 0.5 kg; in the third case, it would increase by 4 kg. What was the total yield of the friends (in kilograms) ...
15
8.59375
31,393
A certain real estate property is holding a lottery for homebuyers, with the following rules: For homeowners who purchase the property, they can randomly draw 2 balls from box $A$, which contains 2 red balls and 2 white balls, and 2 balls from box $B$, which contains 3 red balls and 2 white balls. If all 4 balls drawn ...
3,675
0
31,394
A cubic block with dimensions $n$ by $n$ by $n$ is made up of a collection of $1$ by $1$ by $1$ unit cubes. What is the smallest value of $n$ so that if the outer two layers of unit cubes are removed from the block, more than half the original unit cubes will still remain?
20
17.96875
31,395
Three lines were drawn through the point $X$ in space. These lines crossed some sphere at six points. It turned out that the distances from point $X$ to some five of them are equal to $2$ cm, $3$ cm, $4$ cm, $5$ cm, $6$ cm. What can be the distance from point $X$ to the sixth point? (Alexey Panasenko)
2.4
18.75
31,396
Find the smallest positive integer $n$ that is divisible by $100$ and has exactly $100$ divisors.
162000
6.25
31,397
Given that $x$ and $y$ are positive integers, and $x^2 - y^2 = 53$, find the value of $x^3 - y^3 - 2(x + y) + 10$.
2011
63.28125
31,398
In the diagram below, $WXYZ$ is a trapezoid such that $\overline{WX}\parallel \overline{ZY}$ and $\overline{WY}\perp\overline{ZY}$. If $YZ = 15$, $\tan Z = \frac{4}{3}$, and $\tan X = \frac{3}{2}$, what is the length of $XY$?
\frac{20\sqrt{13}}{3}
21.875
31,399
Solve the following equations: (1) $x^{2}-3x=4$; (2) $x(x-2)+x-2=0$.
-1
0