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Suppose $d$ is a digit. For how many values of $d$ is $2.00d5 > 2.005$?
5
China's space station has entered the formal construction phase. The Tianhe core module, Wentian experimental module, and Mengtian experimental module will all dock in 2022, forming a "T" shaped structure. During the construction phase of the Chinese space station, there are 6 astronauts staying in the space station. It is expected that in a certain construction task, 6 astronauts need to work simultaneously in the Tianhe core module, Wentian experimental module, and Mengtian experimental module. Due to space limitations, each module must have at least 1 person and at most 3 people. The total number of different arrangement plans is ______.
450
A rectangular piece of paper whose length is $\sqrt{3}$ times the width has area $A$. The paper is divided into three equal sections along the opposite lengths, and then a dotted line is drawn from the first divider to the second divider on the opposite side as shown. The paper is then folded flat along this dotted line to create a new shape with area $B$. What is the ratio $\frac{B}{A}$?
\frac{4}{5}
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
Find the area of the triangle with vertices $(2, -3),$ $(1, 4),$ and $(-3, -2).$
17
Find the sum of the first seven prime numbers that have a units digit of 7.
379
Alice and Bob play a game involving a circle whose circumference is divided by 12 equally-spaced points. The points are numbered clockwise, from 1 to 12. Both start on point 12. Alice moves clockwise and Bob, counterclockwise. In a turn of the game, Alice moves 5 points clockwise and Bob moves 9 points counterclockwise. The game ends when they stop on the same point. How many turns will this take?
6
Suppose $a$, $b$, $c$, and $d$ are integers satisfying the equations: $a - b + c = 7$, $b - c + d = 8$, $c - d + a = 5$, and $d - a + b = 4$. What is the value of $a + b + c + d$?
12
The matrices \[\begin{pmatrix} a & 2 \\ 1 & 4 \end{pmatrix} \quad \text{and} \quad \begin{pmatrix} -\frac{2}{7} & \frac{1}{7} \\ b & \frac{3}{14} \end{pmatrix}\]are inverses. Enter the ordered pair $(a,b).$
\left( -3, \frac{1}{14} \right)
Determine the least possible value of $f(1998),$ where $f:\Bbb{N}\to \Bbb{N}$ is a function such that for all $m,n\in {\Bbb N}$, \[f\left( n^{2}f(m)\right) =m\left( f(n)\right) ^{2}. \]
120
Kelly is attempting to unlock her electronic device with a four-digit password. She remembers that she only used digits from 1 to 6, each digit possibly being repeated, and that each odd digit must be followed by an even digit, with no specific rule for the sequences following even digits. How many combinations might Kelly need to consider?
648
For how many integer values of $n$ between 1 and 120 inclusive does the decimal representation of $\frac{n}{120}$ terminate?
40
Consider all 1000-element subsets of the set $\{1, 2, 3, ... , 2015\}$. From each such subset choose the least element. The arithmetic mean of all of these least elements is $\frac{p}{q}$, where $p$ and $q$ are relatively prime positive integers. Find $p + q$. Hint Use the Hockey Stick Identity in the form \[\binom{a}{a} + \binom{a+1}{a} + \binom{a+2}{a} + \dots + \binom{b}{a} = \binom{b+1}{a+1}.\] (This is best proven by a combinatorial argument that coincidentally pertains to the problem: count two ways the number of subsets of the first $(b + 1)$ numbers with $(a + 1)$ elements whose least element is $i$, for $1 \le i \le b - a$.)
431
Given $a$ and $b$ are the roots of the equation $x^2-2cx-5d = 0$, and $c$ and $d$ are the roots of the equation $x^2-2ax-5b=0$, where $a,b,c,d$ are distinct real numbers, find $a+b+c+d$.
30
Find the minimum value of \[2 \cos \theta + \frac{1}{\sin \theta} + \sqrt{2} \tan \theta\]for $0 < \theta < \frac{\pi}{2}.$
3 \sqrt{2}
Mary and Ann are going sledding. Mary slides down a hill that's 630 feet long at a speed of 90 feet/minute. Ann slides down a hill that's 800 feet long at a rate of 40 feet/minute. How much longer does Ann's trip take than Mary?
First find the total time Mary's trip takes: 630 feet / 90 feet/minute = <<630/90=7>>7 minutes Then find the total time Ann's trip takes: 800 feet / 40 feet/minute = <<800/40=20>>20 minutes Then subtract Mary's time from Ann's time to find the difference: 20 minutes - 7 minutes = <<20-7=13>>13 minutes #### 13
The third chick received as much porridge as the first two chicks combined. The fourth chick received as much porridge as the second and third chicks combined. The fifth chick received as much porridge as the third and fourth chicks combined. The sixth chick received as much porridge as the fourth and fifth chicks combined. The seventh chick did not receive any porridge because it ran out. It is known that the fifth chick received 10 grams of porridge. How much porridge did the magpie cook?
40
Evaluate the sum \[\frac{1}{2^1} + \frac{2}{2^2} + \frac{3}{2^3} + \cdots + \frac{k}{2^k} + \cdots \]
2
Suppose two arithmetic sequences $\{a_n\}$ and $\{b_n\}$ have the sum of their first $n$ terms as $S_n$ and $T_n$, respectively. Given that $\frac{S_n}{T_n} = \frac{7n}{n+3}$, find the value of $\frac{a_5}{b_5}$.
\frac{21}{4}
Given a circle $x^2 + (y-1)^2 = 1$ with its tangent line $l$, which intersects the positive x-axis at point A and the positive y-axis at point B. Determine the y-intercept of the tangent line $l$ when the distance AB is minimized.
\frac{3+\sqrt{5}}{2}
No two students in Mrs. Vale's 26-student mathematics class have the same two initials. Each student's first name and last name begin with the same letter. If the letter ``Y'' is considered a vowel, what is the probability of randomly picking a student whose initials are vowels? Express your answer as a common fraction.
\frac{3}{13}
You are given a set of cards labeled from 1 to 100. You wish to make piles of three cards such that in any pile, the number on one of the cards is the product of the numbers on the other two cards. However, no card can be in more than one pile. What is the maximum number of piles you can form at once?
8
We are given 5771 weights weighing 1,2,3,...,5770,5771. We partition the weights into $n$ sets of equal weight. What is the maximal $n$ for which this is possible?
2886
A collection of $n$ squares on the plane is called tri-connected if the following criteria are satisfied: (i) All the squares are congruent. (ii) If two squares have a point $P$ in common, then $P$ is a vertex of each of the squares. (iii) Each square touches exactly three other squares. How many positive integers $n$ are there with $2018 \leq n \leq 3018$, such that there exists a collection of $n$ squares that is tri-connected?
501
Divide every natural number with at least two digits by the sum of its digits! When will the quotient be the largest, and when will it be the smallest?
1.9
A circle is circumscribed around $ABCD$ as follows: [asy] pair pA, pB, pC, pD, pO; pO = (0, 0); pA = pO + dir(-40); pB = pO + dir(40); pC = pO + dir(130); pD = pO + dir(190); draw(pA--pB--pC--pA); draw(pA--pD--pC--pA); label("$A$", pA, SE); label("$B$", pB, NE); label("$C$", pC, NW); label("$D$", pD, SW); draw(circle(pO, 1)); label("$30^\circ$", pA + dir(150) * .45); label("$40^\circ$", pC + dir(-20) * .35); [/asy] How many degrees are in $\angle CAB + \angle ACD$?
110^\circ
Let $N$ be the largest integer whose square has exactly $3$ digits when written in base 9. What is $N$, expressed in base 9?
28_9
Using the vertices of a single rectangular solid (cuboid), how many different pyramids can be formed?
106
Find the difference between the largest integer solution of the equation \(\lfloor \frac{x}{3} \rfloor = 102\) and the smallest integer solution of the equation \(\lfloor \frac{x}{3} \rfloor = -102\).
614
Mr. Rainwater has some goats, 9 cows and some chickens. He has 4 times as many goats as cows and 2 times as many goats as chickens. How many chickens does he have?
Let X be the number of chickens Mr. Rainwater has. He has 4 goats/cow * 9 cows = <<4*9=36>>36 goats on his farm. So he has 36 goats / 2 goats/chicken = <<36/2=18>>18 chickens. #### 18
In the diagram below, $ABCD$ is a trapezoid such that $\overline{AB}\parallel \overline{CD}$ and $\overline{AC}\perp\overline{CD}$. If $CD = 20$, $\tan D = 2$, and $\tan B = 2.5$, then what is $BC$? [asy] pair A,B,C,D; C = (0,0); D = (20,0); A = (20,40); B= (30,40); draw(A--B--C--D--A); label("$A$",A,N); label("$B$",B,N); label("$C$",C,S); label("$D$",D,S); [/asy]
4\sqrt{116}
Let \( P \) be the parabola with equation \( y = x^2 \) and let \( Q = (10, 6) \). There are real numbers \( r \) and \( s \) such that the line through \( Q \) with slope \( m \) does not intersect \( P \) if and only if \( r < m < s \). What is \( r + s \)?
40
Given a right triangle \(ABC\) with a right angle at \(A\). On the leg \(AC\), a point \(D\) is marked such that \(AD:DC = 1:3\). Circles \(\Gamma_1\) and \(\Gamma_2\) are then drawn with centers at \(A\) and \(C\) respectively, both passing through point \(D\). \(\Gamma_2\) intersects the hypotenuse at point \(E\). Another circle \(\Gamma_3\) with center at \(B\) and radius \(BE\) intersects \(\Gamma_1\) inside the triangle at a point \(F\) such that \(\angle AFB\) is a right angle. Find \(BC\), given that \(AB = 5\).
13
Find the largest natural number in which each digit, starting from the third, is equal to the sum of all previous digits of the number.
101248
From 5 differently colored balls, select 4 balls to place into 3 distinct boxes, with the requirement that no box is left empty. The total number of different ways to do this is ______. (Answer with a number)
180
Let $x, y, z$ be positive real numbers such that $x + 2y + 3z = 1$. Find the maximum value of $x^2 y^2 z$.
\frac{4}{16807}
A father is building a playset for his son and needs to purchase lumber, nails, and fabric. When he started planning the project, the necessary lumber cost $450, the nails cost $30, and the fabric cost $80. However, recent economic inflation has caused the price of lumber to increase by 20%, the price of nails to increase by 10%, and the price of fabric to increase by 5%. In dollars, how much more money will it cost to complete the project now (after inflation) than it would have when the father began planning?
First, the initial, pre-inflation, cost of the project was 450 + 30 + 80 = $<<450+30+80=560>>560. Then, the price of the lumber increased to 450*1.20 = $<<450*1.20=540>>540. Similarly, the price of the nails increased to 30*1.10 = $<<30*1.10=33>>33. And the price of the fabric increased to 80*1.05 = $<<80*1.05=84>>84. Therefore, the new, post-inflation, cost of the project is 540 + 33 + 84 = $<<540+33+84=657>>657. Thus, the cost has increased by 657 - 560 = $<<657-560=97>>97. #### 97
To increase her water intake to the recommended level by her doctor, Happy has to take 40% more cups of water than she takes now. If she is currently drinking 15 cups of water every week, what's the recommended number of cups per week?
Happy has to take 40/100 * 15 = <<40/100*15=6>>6 more cups of water than she takes currently to reach the recommended water intake levels by her doctor. In total, she is supposed to drink 6+15 = <<6+15=21>>21 cups of water every week. #### 21
Determine the residue of $-811\pmod{24}$. Your answer should be an integer in the range $0,1,2,\ldots,22,23$.
5
If the shortest chord is cut by the line $y = kx + 1$ on the circle $C: x^2 + y^2 - 2x - 3 = 0$, then $k = \boxed{\_\_\_\_\_\_\_\_}$.
-1
The table shows the vertical drops of six roller coasters in Fibonacci Fun Park: \begin{tabular}{|l|c|} \hline Speed Demon & 150 feet \\ \hline Looper & 230 feet \\ \hline Dare Devil & 160 feet \\ \hline Giant Drop & 190 feet \\ \hline Sky Scream & 210 feet \\ \hline Hell Spiral & 180 feet \\ \hline \end{tabular} What is the positive difference between the mean and the median of these values?
1.67
Given the system of equations \begin{align*} xy &= 6 - 2x - 3y,\\ yz &= 6 - 4y - 2z,\\ xz &= 30 - 4x - 3z, \end{align*}find the positive solution of $x$.
3
Given that \( n! \) is evenly divisible by \( 1 + 2 + \cdots + n \), find the number of positive integers \( n \) less than or equal to 50.
36
Four people, A, B, C, and D, participated in an exam. The combined scores of A and B are 17 points higher than the combined scores of C and D. A scored 4 points less than B, and C scored 5 points more than D. How many points higher is the highest score compared to the lowest score among the four?
13
Determine the value of the infinite product $(2^{1/3})(4^{1/9})(8^{1/27})(16^{1/81}) \dotsm.$ Enter your answer in the form "\sqrt[a]{b}", which stands for $\sqrt[a]{b}.$
\sqrt[4]{8}
Given $f\left(\alpha \right)=\frac{\mathrm{sin}\left(\pi -\alpha \right)\mathrm{cos}\left(2\pi -\alpha \right)\mathrm{cos}\left(-\alpha +\frac{3\pi }{2}\right)}{\mathrm{cos}\left(\frac{\pi }{2}-\alpha \right)\mathrm{sin}\left(-\pi -\alpha \right)}$. (1) Simplify $f(\alpha )$. (2) If $\alpha$ is an angle in the third quadrant and $\mathrm{cos}(\alpha -\frac{3\pi }{2})=\frac{1}{5}$, find the value of $f(\alpha )$.
\frac{2\sqrt{6}}{5}
Juan, Carlos and Manu take turns flipping a coin in their respective order. The first one to flip heads wins. What is the probability that Manu will win? Express your answer as a common fraction.
\frac{1}{7}
Calculate the definite integral: $$ \int_{2 \operatorname{arctg} \frac{1}{3}}^{2 \operatorname{arctg} \frac{1}{2}} \frac{d x}{\sin x(1-\sin x)} $$
\ln 3 - \ln 2 + 1
The sequence $\{a_n\}$ satisfies $a_n=13-3n$, $b_n=a_n⋅a_{n+1}⋅a_{n+2}$, $S_n$ is the sum of the first $n$ terms of $\{b_n\}$. Find the maximum value of $S_n$.
310
In a given plane, points $A$ and $B$ are $10$ units apart. How many points $C$ are there in the plane such that the perimeter of $\triangle ABC$ is $50$ units and the area of $\triangle ABC$ is $100$ square units?
2
Let $A=(0,1),$ $B=(2,5),$ $C=(5,2),$ and $D=(7,0).$ A figure is created by connecting $A$ to $B,$ $B$ to $C,$ $C$ to $D,$ and $D$ to $A.$ The perimeter of $ABCD$ can be expressed in the form $a\sqrt2+b\sqrt{5}$ with $a$ and $b$ integers. What is the sum of $a$ and $b$?
12
Let a constant $a$ make the equation $\sin x + \sqrt{3}\cos x = a$ have exactly three different solutions $x_{1}$, $x_{2}$, $x_{3}$ in the closed interval $\left[0,2\pi \right]$. The set of real numbers for $a$ is ____.
\{\sqrt{3}\}
In a circle, parallel chords of lengths 5, 12, and 13 determine central angles of $\theta$, $\phi$, and $\theta + \phi$ radians, respectively, where $\theta + \phi < \pi$. If $\sin \theta$, which is a positive rational number, is expressed as a fraction in lowest terms, what is the sum of its numerator and denominator?
18
Lyka wants to buy a smartphone worth $160 but she only has $40 at the moment. She plans to save an equal amount of money per week for two months for the remaining amount that she needs. How much should she save per week?
Lyka has to save a total of $160 - $40 = $<<160-40=120>>120 for two months. There are 2 x 4 = <<2*4=8>>8 weeks in two months. Hence, Lyka needs to save $120/8 = $<<120/8=15>>15 per week. #### 15
What is the greatest possible positive integer value of $x$ if $\displaystyle\frac{x^4}{x^2} < 10$?
3
Yann writes down the first $n$ consecutive positive integers, $1,2,3,4, \ldots, n-1, n$. He removes four different integers $p, q, r, s$ from the list. At least three of $p, q, r, s$ are consecutive and $100<p<q<r<s$. The average of the integers remaining in the list is 89.5625. What is the number of possible values of $s$?
22
Compute $\tan 20^\circ + 4 \sin 20^\circ.$
\sqrt{3}
Consider the system of equations \[ 8x - 6y = c, \] \[ 12y - 18x = d. \] If this system has a solution \((x, y)\) where both \(x\) and \(y\) are nonzero, find the value of \(\frac{c}{d}\), assuming \(d\) is nonzero.
-\frac{4}{9}
A number is chosen at random from the set of consecutive natural numbers $\{1, 2, 3, \ldots, 24\}$. What is the probability that the number chosen is a factor of $4!$? Express your answer as a common fraction.
\frac{1}{3}
Given $\overrightarrow{a}=(-3,4)$, $\overrightarrow{b}=(5,2)$, find $|\overrightarrow{a}|$, $|\overrightarrow{b}|$, and $\overrightarrow{a}\cdot \overrightarrow{b}$.
-7
If $f(x)$ is a function, then we define the function $f^{(n)}(x)$ to be the result of $n$ applications of $f$ to $x$, where $n$ is a positive integer. For example, $f^{(3)}(x)=f(f(f(x)))$. We define the $\textit{order}$ of an input $x$ with respect to $f$ to be the smallest positive integer $m$ such that $f^{(m)}(x)=x$. Now suppose $f(x)$ is the function defined as the remainder when $x^2$ is divided by $11$. What is the order of $5$ with respect to this function $f$?
4
A geometric sequence of positive integers is formed for which the first term is 3 and the fourth term is 192. What is the third term of the sequence?
48
Consider two lines $p$ and $q$ in a coordinate plane with equations $y = -3x + 9$ and $y = -6x + 9$, respectively. Determine the probability that a point randomly selected in the first quadrant and below line $p$ will fall between $p$ and $q$.
0.5
The following bar graph represents the length (in letters) of the names of 19 people. What is the median length of these names?
4
In the next 3 days, a meteorological station forecasts the weather with an accuracy rate of 0.8. The probability that the forecast is accurate for at least two consecutive days is ___.
0.768
A gardener plans to place potted plants along both sides of a 150-meter-long path (including at both ends), with one pot every 2 meters. In total, \_\_\_\_\_\_ pots are needed.
152
Let $n$ be the answer to this problem. Hexagon $ABCDEF$ is inscribed in a circle of radius 90. The area of $ABCDEF$ is $8n$, $AB=BC=DE=EF$, and $CD=FA$. Find the area of triangle $ABC$.
2592
What is the remainder when the sum of the first five primes is divided by the sixth prime?
2
Omi is twice as old as Kimiko. Arlette is 3/4 times as old as Kimiko. If Kimiko is 28 years old, calculate the average age of the three?
If Kimiko is 28, Omi is 2 * 28 years = <<28*2=56>>56 years old. Arlette is 3/4 * 28 years = <<3/4*28=21>>21 years old. If you add up their ages, it sums to 21 years + 56 years + 28 years = <<21+56+28=105>>105 years The average age for the three is 105 years / 3 people = <<105/3=35>>35 years/person #### 35
Rectangle \( EFGH \) is 10 cm by 6 cm. \( P \) is the midpoint of \( \overline{EF} \), and \( Q \) is the midpoint of \( \overline{GH} \). Calculate the area of region \( EPGQ \). **
30
Find the smallest positive number $\lambda$ such that for any triangle with side lengths $a, b, c$, given $a \geqslant \frac{b+c}{3}$, it holds that $$ a c + b c - c^{2} \leqslant \lambda\left(a^{2} + b^{2} + 3 c^{2} + 2 a b - 4 b c\right). $$
\frac{2\sqrt{2} + 1}{7}
There are 32 ones written on the board. Each minute, Carlsson erases any two numbers, writes their sum on the board, and then eats an amount of candy equal to the product of the two erased numbers. What is the maximum number of candies he could eat in 32 minutes?
496
Given non-zero vectors \\(a\\) and \\(b\\) satisfying \\(|b|=2|a|\\) and \\(a \perp (\sqrt{3}a+b)\\), find the angle between \\(a\\) and \\(b\\).
\dfrac{5\pi}{6}
Five dice with faces numbered 1 through 6 are stacked in a similar manner to the original problem. Ten of the thirty faces are visible, leaving twenty faces hidden. The visible numbers are 1, 2, 2, 3, 3, 3, 4, 4, 5, and 6. What is the total number of dots NOT visible in this view?
72
A particular convex polygon with seven sides has exactly one right angle. How many diagonals does this seven-sided polygon have?
14
Given vectors $\overrightarrow{a}=(x,3)$ and $\overrightarrow{b}=(-1,y-1)$, and $\overrightarrow{a}+2\overrightarrow{b}=(0,1)$, find the value of $|\overrightarrow{a}+\overrightarrow{b}|$.
\sqrt{5}
If $x$ and $y$ are positive integers with $3^{x} 5^{y} = 225$, what is the value of $x + y$?
4
What is the positive difference between the median and the mode of the data given in the stem and leaf plot below? In this plot $5|8$ represents $58.$ \begin{tabular}{|c|c|}\hline \textbf{Tens} & \textbf{Units} \\ \hline 1 & $2 \hspace{2mm} 3 \hspace{2mm} 4 \hspace{2mm} 5 \hspace{2mm} 5$ \\ \hline 2 & $2 \hspace{2mm} 2 \hspace{2mm} 2 \hspace{2mm} \hspace{2mm} \hspace{2mm} \hspace{1.5mm}$ \\ \hline 3 & $1 \hspace{2mm} 1 \hspace{2mm} 8 \hspace{2mm} 9 \hspace{2mm} \hspace{1.9mm}$ \\ \hline 4 & $ 0 \hspace{2mm} 1 \hspace{2mm} 2 \hspace{2mm} 3 \hspace{2mm} \hspace{1.9mm}$ \\ \hline 5 & $ 2 \hspace{2mm} 8 \hspace{2mm} 9 \hspace{2mm} \hspace{2mm} \hspace{2mm} \hspace{1.5mm}$ \\\hline \end{tabular}
9
Compute \[ \left\lfloor \dfrac {1007^3}{1005 \cdot 1006} - \dfrac {1005^3}{1006 \cdot 1007} + 5 \right\rfloor,\] where $\lfloor x \rfloor$ denotes the greatest integer less than or equal to $x.$
12
In triangle $ABC$ , $AB=13$ , $BC=14$ and $CA=15$ . Segment $BC$ is split into $n+1$ congruent segments by $n$ points. Among these points are the feet of the altitude, median, and angle bisector from $A$ . Find the smallest possible value of $n$ . *Proposed by Evan Chen*
27
The figure shown consists of a right triangle and two squares. If the figure's total area equals 850 square inches, what is the value of $x$ in inches? [asy] unitsize(5mm); defaultpen(linewidth(.7pt)+fontsize(10pt)); draw((0,5)--(0,-2)--(-2,-2)--(-2,0)--(5,0)--(5,5)--cycle--(-2,0)); draw(scale(0.2)*((-1,0)--(-1,1)--(1,1)--(1,0))); label("$2x$",(-1,0),S); label("$5x$",(0,2.5),E); [/asy]
5
In trapezoid $ABCD$ the lengths of the bases $AB$ and $CD$ are 8 and 17 respectively. The legs of the trapezoid are extended beyond $A$ and $B$ to meet at point $E$. What is the ratio of the area of triangle $EAB$ to the area of trapezoid $ABCD$? Express your answer as a common fraction.
\frac{64}{225}
$18 \cdot 92$ A square $ABCD$ has side lengths of 1. Points $E$ and $F$ lie on sides $AB$ and $AD$ respectively, such that $AE = AF$. If the quadrilateral $CDFE$ has the maximum area, what is the maximum area?
$\frac{5}{8}$
Bob enters cycling competitions every single week and hopes to win the 100 dollar grand prize each time. For the first 2 weeks, he managed first place and got 100 dollars each week. He is saving up for a puppy that costs 1000 dollars. What is the minimum number of additional weeks Bob must win first place?
Two weeks already passed and Bob has 200 dollars. Bob needs 1000-200=<<1000-200=800>>800 more dollars. Bob needs to win the competition for at least 800/100=<<800/100=8>>8 more weeks. #### 8
Compute the sum of the geometric series $-1 + 2 - 4 + 8 - \cdots + 512$.
341
If the equation $\frac{m}{x-3}-\frac{1}{3-x}=2$ has a positive root with respect to $x$, then the value of $m$ is ______.
-1
What is $2^{16} \div 16^2$? Write your answer as an integer.
256
Find the minimum value of \[ x^3 + 9x + \frac{81}{x^4} \] for \( x > 0 \).
21
Suppose $\cos R = \frac{4}{9}$ in the diagram below. What is $QS$? [asy] pair Q,R,S; S = (0,0); Q = (sqrt(65),0); R = (sqrt(65),-4); draw(S--Q--R--S); draw(rightanglemark(S,Q,R,13)); label("$S$",S,NW); label("$Q$",Q,NE); label("$R$",R,SE); label("$9$",(R+S)/2,SW); [/asy]
\sqrt{65}
Carlo has a music recital next week. He practiced twice as long on Monday as on Tuesday. On Tuesday, he practiced 10 minutes less than on Wednesday. On Wednesday, he practiced 5 minutes more than on Thursday. On Thursday, he practiced for 50 minutes. If he needs to practice for a total of 5 hours that week, how long should Carlo practice on Friday?
On Wednesday, Carlo practiced for 50 + 5 = <<50+5=55>>55 minutes. On Tuesday, he practiced for 55 - 10 = <<55-10=45>>45 minutes. On Monday, he practiced for 45 x 2 = <<45*2=90>>90 minutes. So, Carlo practiced for a total of 90 + 45 + 55 + 50 = <<90+45+55+50=240>>240 minutes from Monday to Thursday. He needs to practice for a total of 60 x 5 = <<60*5=300>>300 minutes. Therefore, he should practice for 300 - 240 = <<300-240=60>>60 minutes on Friday. #### 60
Given a function $f(x)$ defined on $\mathbb{R}$ that is an odd function, and the period of the function $f(2x+1)$ is 5, if $f(1) = 5$, calculate the value of $f(2009) + f(2010)$.
-5
The line $y = a$ intersects the curves $y = 2(x + 1)$ and $y = x + \ln x$ at points $A$ and $B$, respectively. Find the minimum value of $|AB|$.
\frac{3}{2}
A two-inch cube ($2\times2\times2$) of silver weighs 3 pounds and is worth $\$200$. How much is a three-inch cube of silver worth? Round your answer to the nearest dollar.
\$675
The numbers $1,...,100$ are written on the board. Tzvi wants to colour $N$ numbers in blue, such that any arithmetic progression of length 10 consisting of numbers written on the board will contain blue number. What is the least possible value of $N$ ?
11
In this problem assume $s_{1}=3$ and $s_{2}=2$. Determine, with proof, the nonnegative integer $k$ with the following property: 1. For every board configuration with strictly fewer than $k$ blank squares, the first player wins with probability strictly greater than $\frac{1}{2}$; but 2. there exists a board configuration with exactly $k$ blank squares for which the second player wins with probability strictly greater than $\frac{1}{2}$.
\[ k = 3 \]
How many two-digit numbers have digits whose sum is a prime number?
31
If $(1-2)^{9}=a_{9}x^{9}+a_{8}x^{8}+\ldots+a_{1}x+a_{0}$, then the sum of $a_1+a_2+\ldots+a$ is \_\_\_\_\_\_.
-2
Christina and her friend are driving across the state. When Christina is driving the speed limit is 30 miles per hour. When her friend is driving, the speed limit is 40 miles per hour. The drive is 210 miles total. If her friend drives for 3 hours and both drive at the speed limit, how many minutes will Christina drive?
The friend drives 40*3=<<40*3=120>>120 miles. Thus, Christina drives 210-120 =<<210-120=90>>90 miles. Since the speed limit is 30 miles per hour when Christina is driving, she drives for 90/30=<<90/30=3>>3 hours. Thus, she drives for 3*60=<<3*60=180>>180 minutes. #### 180
Miki has a dozen oranges of the same size and a dozen pears of the same size. Miki uses her juicer to extract 8 ounces of pear juice from 3 pears and 8 ounces of orange juice from 2 oranges. She makes a pear-orange juice blend from an equal number of pears and oranges. What percent of the blend is pear juice?
40
The length of a rectangle is four times its width. If the area is 100 m2. what is the length of the rectangle?
Let L be the length and W be the width of the rectangle. Hence L = 4* W We now use the area to write 80 = L * W Substitute L by 4 W in the equation above 80 = 4*W × W = 4 W^2 Solve for W and find L 4 W^2 = 100 W^2 = 25, W = 5 and L = 4*5 = <<4*5=20>>20 m #### 20