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math
Given $\lfloor x \rfloor$ be the greatest integer less than or equal to $x$, determine the number of real solutions to $4x^2-40\lfloor x \rfloor +51=0$.
4
49
1
math
If $x$ satisfies $\left(x-2\right)^{x+1}=1$, then the value of the integer $x$ is ______.
-1, 3, 1
32
8
math
Palindromic primes are two-digit prime numbers such that the number formed when the digits are reversed is also prime. What is the sum of all palindromic primes less than 50?
109
41
3
math
Given the function $f(x)= \frac {2x^{2}}{e}+ \frac {e^{2}}{x}$, $g(x)=3e\ln x$, where $e$ is the base of the natural logarithm. - (I) Discuss the monotonicity of the function $f(x)$. - (II) Determine whether the curve $y=f(x)$ and $y=g(x)$ have a common point and a common tangent line at that point. If such a point exi...
y=3x
126
4
math
In a fuel tank, there are 40 liters of oil. The oil flows out of the tank uniformly at a rate of 0.2 liters per minute. Determine the function relationship between the remaining oil quantity Q (in liters) in the tank and the time t (in minutes) of outflow.
Q=40-0.2t
63
9
math
There are lindens and birches planted around the house, with their total quantity being more than 14. If the number of lindens is doubled and the number of birches is increased by 18, there will be more birches than lindens. If the number of birches is doubled without changing the number of lindens, there will now be m...
11 \text{ limes and } 5 \text{ birch trees}
99
18
math
Given an acute triangle $ABC$ with sides $a$, $b$, $c$ opposite to angles $A$, $B$, $C$ respectively. Choose any one of the three conditions below to solve the following problems (if multiple conditions are used, follow the first solution): $(1)$ Find angle $B$; $(2)$ If $b=2$ and the area of triangle $ABC$ is $\sqrt{3...
2
98
1
math
In rectangle $ABCD$, $AB = 10$ cm, $BC = 5$ cm, and $DG = DH$. The area of triangle $DGH$ is one-fifth the area of rectangle $ABCD$. Determine the length in centimeters of segment $GH$. Express your answer in simplest radical form. [asy] draw((0,0)--(0,50)--(100,50)--(100,0)--cycle); draw((40,50)--(100,20)); label("$A...
GH = 2\sqrt{10} \text{ cm}
196
15
math
Find \( n \) if \( n\cdot (n+1)! + (n+1)! = 5040 \), where \( n! = n\cdot (n-1)\cdot (n-2)\cdots 2\cdot 1 \).
5
58
1
math
Given that Sarah and Jill start a swimming race from opposite ends of a 50-meter pool, and they cross paths two minutes after they start, determine the time it takes for them to cross paths for the second time.
6
45
1
math
Quadrilateral $ABCD$ has $AB = BC = CD$, $m\angle ABC = 70^\circ$ and $m\angle BCD = 170^\circ$. What is the degree measure of $\angle BAD$?
85
53
2
math
There is a cube of size \(10 \times 10 \times 10\) made up of small unit cubes. A grasshopper is sitting at the center \(O\) of one of the corner cubes. It can jump to the center of a cube that shares a face with the one in which the grasshopper is currently located, provided that the distance to point \(O\) increases....
\frac{27!}{(9!)^3}
101
13
math
If $\cos(α + \frac{π}{3}) = -\frac{\sqrt{3}}{3}$, find the value of $\sin α$.
\frac{\sqrt{6} + 3}{6}
34
13
math
Find the coefficient of the $x^2$ term in the expansion of $(2x^3 + 5x^2 - 3x + 1)(3x^2 - 9x - 5)$.
5
47
1
math
Suppose the line $l$: $\begin{cases} x=1+\frac{1}{2}t \\ y=\frac{\sqrt{3}}{2}t \end{cases} (t \text{ is the parameter})$, and the curve $C_{1}$: $\begin{cases} x=\cos \theta \\ y=\sin \theta \end{cases} (\theta \text{ is the parameter})$. (1) Let $l$ intersect $C_{1}$ at two points $A$ and $B$, find $|AB|$. (2) If th...
\frac{\sqrt{6}}{4}(\sqrt{2}-1)
214
17
math
Given the function $f(x)=a^2x^2-2ax+1$, if the proposition "$\forall x \in (0,1)$, $f(x) \neq 0$" is a false proposition, then the range of the real number $a$ is __________.
a > 1
63
4
math
The tangent line to the curve $y=x^3+x-2$ at point P is parallel to the line $y=4x-1$. Find the equation of this tangent line.
y=4x-4 \text{ or } y=4x
39
15
math
A batch of parts is divided into three grades, with 24 first-grade parts and 36 second-grade parts. Using stratified sampling to draw a sample of size 20, if exactly 10 third-grade parts are drawn, then the number of third-grade parts in this batch is $\_\_\_\_\_\_\_$, and the number of second-grade parts drawn in the ...
6
95
1
math
Find all real solutions to the system of equations $$ \begin{aligned} & x^{2}+y^{2}+z^{2}=1, \\ & x^{3}+y^{3}+z^{3}=1 . \end{aligned} $$
(1, 0, 0), (0, 1, 0), (0, 0, 1)
58
27
math
Given the complex number $Z=\frac{-2+i}{i^{2018}}$, find the imaginary part of the conjugate of the complex number $Z$, denoted as $\overline{Z}$.
1
45
1
math
Given the fraction $\frac{7}{125}$, convert it to a decimal.
0.056
19
5
math
A chord of the parabola $y^2=4x$ intersects the parabola at points A($x_1$, $y_1$) and B($x_2$, $y_2$). If the length of the chord AB is 7, find the distance from the midpoint M of the chord to the parabola's directrix.
\frac{7}{2}
77
7
math
What is the angle opposite side \( c \) in a triangle with sides \( a, b, c \), perimeter \( 2s \), and area \( T \), if $$ T+\frac{a b}{2}=s(s-c) ? $$
45^\circ
55
4
math
Compute $\arccos (\sin 3).$ All functions are in radians.
3 - \frac{\pi}{2}
17
9
math
In the sequence $\{a_{n}\}$, $a_{1}=18$, $a_{2}=24$, $a_{n+2}-a_{n}=-6$. $(1)$ Find the general formula for $\{a_{n}\}$; $(2)$ Let the sum of the first $n$ terms of the sequence $\{a_{n}\}$ be $S_{n}$, find the maximum value of $S_{n}$.
96
100
2
math
A bag contains 4 blue, 3 green, and 5 red chips. If the 12 chips are randomly drawn from the bag, one at a time and without replacement, what is the probability that the chips are drawn in such a way that the 4 blue chips are drawn consecutively, the 3 green chips are drawn consecutively, and the 5 red chips are drawn ...
\frac{1}{4620}
104
10
math
Rotate the parabola $y=3x^2-6x+5$ around its vertex by 180°, then translate it along the axis of symmetry to obtain a new parabola that intersects the line $y=-x-2$ at the point $(2, m)$. The equation of the new parabola is ____.
y=-3x^2+6x-4
74
11
math
The quadrilateral $ABCD$ has the following equality $\angle ABC=\angle BCD=150^{\circ}$. Moreover, $AB=18$ and $BC=24$, the equilateral triangles $\triangle APB,\triangle BQC,\triangle CRD$ are drawn outside the quadrilateral. If $P(X)$ is the perimeter of the polygon $X$, then the following equality is true $P(APQRD)=...
10
109
2
math
A right frustum oil tank can hold 190 liters of kerosene. Given that the lengths of its top and bottom edges are 60cm and 40cm respectively, its depth is \_\_\_\_\_\_\_\_.
75\text{cm}
52
7
math
Determine the angle of inclination, in terms of inverse trigonometric functions, for the line given by the equation $2x+y-1=0$.
\alpha = \pi - \arctan(2)
32
13
math
Given a sequence $\{a_n\}$ whose sum of the first $n$ terms is $S_n$, $a_1=\frac{1}{2}$, and $2a_{n+1}=S_n+1$. (Ⅰ) Find the values of $a_2$ and $a_3$; (Ⅱ) Let $b_n=2a_n-2n-1$, find the sum of the first $n$ terms of the sequence $\{b_n\}$, denoted as $T_n$.
2\cdot\left(\frac{3}{2}\right)^{n}-n^2-2n-2
115
25
math
Evaluate \[\frac{3}{\log_3{1000^4}} + \frac{4}{\log_7{1000^4}}\], giving your answer as a fraction in lowest terms.
\log_{10} (3^{1/4} \cdot 7^{1/3})
49
22
math
Given an arithmetic sequence $\{a_n\}$ with a common difference $d > 0$, and $a_2$, $a_5-1$, $a_{10}$ form a geometric sequence. The first term of the sequence is $a_1=5$, and $S_n$ is the sum of the first $n$ terms of the sequence. Find the minimum value of $\frac{2S_n+n+32}{a_n+1}$.
\frac{20}{3}
99
8
math
In $\triangle ABC$, the sides opposite to angles $A$, $B$, and $C$ are $a$, $b$, and $c$ respectively. Given that $c= \sqrt {3}$, and $(\sqrt {3}+a)(sinC-sinA)=(a+b)sinB$, find the maximum value of the perimeter of $\triangle ABC$.
2+ \sqrt {3}
78
7
math
Given that $m \angle A= 60^\circ$, $BC=12$ units, $\overline{BD} \perp \overline{AC}$, $\overline{CE} \perp \overline{AB}$ and $m \angle DBC = 3m \angle ECB$, the length of segment $EC$ can be expressed in the form $a(\sqrt{b}+\sqrt{c})$ units where $b$ and $c$ have no perfect-square factors. What is the value of $a+b...
11
244
2
math
Given that the ceiling is 3.0 meters above the ground, Bob is 1.8 meters tall and can reach 50 centimeters above the top of his head, and the light fixture is 15 centimeters below the ceiling, calculate the height of the box in centimeters.
55
61
2
math
Given $f(x)=\frac{[\sin(\frac{\pi}{2}-x)\tan(\pi-x)]^{2}-1}{4\sin(\frac{3\pi}{2}+x)+\cos(\pi-x)+\cos(2\pi-x)}$, (1) Find $f(-1860^{\circ})$; (2) If the equation $f^{2}(x)+(1+\frac{1}{2}a)\sin x+2a=0$ has two roots in $x\in[\frac{\pi}{6},\frac{3\pi}{4}]$, find the range of the real number $a$; (3) Find the maximum value...
y_\text{max}=2
175
7
math
Given a function $f(x)$ defined on the domain $\mathbb{R}$ that satisfies $f(-x) + f(x) = 0$. If $f(x)$ is a decreasing function on $(0, +\infty)$ and $f(-2) = 0$, find the range of values for $x$ such that $(x-1)f(x) > 0$.
(-2,0)∪(1,2)
82
11
math
Given the function $f(x+2) - f(x) = 2f(1)$, and the graph of $y=f(x-1)$ is symmetric about $x=1$, with $f(0)=2$, calculate $f(2015) + f(2016)$.
2
66
1
math
A community plans to invest $500$ yuan to purchase three types of books, A, B, and C, with type A costing $30$ yuan per book, type B costing $25$ yuan per book, and type C costing $20$ yuan per book. Given that the community must buy at least $5$ books of type A and at most $6$ books of type A, determine the number of ...
6
97
1
math
We place labeled points on a circle as follows. At step 1, take two points at opposite ends of a diameter and label them both 1. At step \( n > 1 \), place a point at the midpoint of each arc created at step \( n-1 \) and label it with the sum of the labels at the two adjacent points. What is the total sum of the label...
2 \times 3^{n-1}
87
10
math
Let $x,$ $y,$ and $z$ be angles such that \begin{align*} \sin x &= \cot y, \\ \sin y &= \cot z, \\ \sin z &= \cot x. \end{align*} Find the minimum possible value of $\cos x.$
\sqrt{\frac{3 - \sqrt{5}}{2}}
64
15
math
Given that the function $f(x)$ defined on $[0,+\infty)$ satisfies $f(x)=2f(x+2)$, and when $x\in[0,2)$, $f(x)=-2x^{2}+4x$. Let the maximum value of $f(x)$ on $[2n-2,2n)$ be $a_{n}(n\in\mathbb{N}^{*})$, calculate the sum of the first $n$ terms of $\{a_{n}\}$.
4- \frac {1}{2^{n-2}}
114
13
math
Let $(x,y,z)$ be an ordered triplet of real numbers that satisfies the following system of equations: \begin{align*}x+y^2+z^4&=0,y+z^2+x^4&=0,z+x^2+y^4&=0.\end{align*} If $m$ is the minimum possible value of $\lfloor x^3+y^3+z^3\rfloor$ , find the modulo $2007$ residue of $m$ .
2004
113
4
math
The ratio $AC:CB$ is $3:4$, in $\triangle ABC$. The external angle bisector of $\angle C$ intersects the extension of $BA$ at $P$, where $A$ is between $P$ and $B$. Find the ratio $PA:AB$.
3:1
60
3
math
Given a triangle $\Delta ABC$ where $CD$ is the altitude of length 1 centimeter and splits $\Delta ABC$ into two 45-45-90 triangles, find the area of $\Delta ABC$.
\sqrt{2}
47
5
math
For the set $A=\{a_1, a_2, \ldots, a_n\}$ ($n \in \mathbb{N}^*$, $n \geq 3$), define the set $S=\{x | x=a_i+a_j, 1 \leq i < j \leq n\}$, and denote the number of elements in set $S$ as $S(A)$. (1) If set $A=\{1, 2, 3, 4\}$, then $S(A)=$ \_\_\_\_\_\_ . (2) If $a_1, a_2, \ldots, a_n$ form an arithmetic sequence with ...
5, 2n-3
185
7
math
Given the 20 vertices of a regular 20-sided polygon inscribed in the unit circle on the complex plane, denoted as \( z_{1}, z_{2}, \cdots, z_{20} \), determine the number of distinct points corresponding to the complex numbers \( z_{1}^{2010.5}, z_{2}^{2005}, \cdots, z_{20}^{2005} \).
4
99
1
math
For some positive integer \( n \), the number \( 210n^3 \) has \( 210 \) positive integer divisors, including \( 1 \) and the number \( 210n^3 \). How many positive integer divisors does the number \( 289n^5 \) have?
108
73
3
math
Given the function $f(x)=x+\dfrac{a}{x}+a^{2}-2$ ($a\in \mathbb{R}$). $(1)$ If $f(x)$ is an odd function, and it is increasing on the interval $(0,+\infty)$, find the value of $a$; $(2)$ If the equation $|\log_{8}(x+1)|-a^{2}+f(1)=0$ has two different real roots $m$, $n$ in the interval $(-1,1)$, find the range of $a...
-1
148
2
math
If the algebraic expression $\frac{(x-1)^{0}}{\sqrt{x+2}}$ is meaningful, then the range of real number $x$ is ____.
x > -2 \quad \text{and} \quad x \neq 1
37
19
math
A rectangle \( P Q R S \) has side-lengths \( a \) and \( b \), with \( a < b \). The rectangle \( P T U V \) has side-lengths \( c \) and \( d \), with \( c < d \). Also, \( a < d \) and \( c < b \), as shown. The sides \( R S \) and \( T U \) cross at \( X \). Which of these conditions guarantees that \( Q, X \), and...
\frac{a}{d} + \frac{c}{b} = 1
217
18
math
The equation of circle $O$ is ${x}^{2}+{y}^{2}=9$, and $P$ is a moving point on circle $O$. If the perpendicular bisector of segment $OP$ is always covered by the plane region $|x|+|y|\geqslant m$, then the range of values for the real number $m$ is.
(-\infty, \dfrac{3}{2}]
81
13
math
Let \(a\) and \(b\) be the roots of the equation \(x^2 - mx + 3 = 0.\) Suppose that \(a^2 + (1/b)\) and \(b^2 + (1/a)\) are the roots of the equation \(x^2 - px + r = 0.\) Determine the value of \(r.\)
\frac{46}{3}
78
8
math
In \\(\triangle ABC\\), the sides opposite to angles \\(A\\), \\(B\\), and \\(C\\) are \\(a\\), \\(b\\), and \\(c\\) respectively, and it is given that \\(b\cos C = 3a\cos B - c\cos B\\). \\((1)\\) Find the value of \\(\cos B\\); \\((2)\\) If \\(\overrightarrow{BA} \cdot \overrightarrow{BC} = 2\\) and \\(b = 2\sqrt{2...
a = c = \sqrt{6}
143
9
math
Let $S$ be a square one of whose sides has a length of $\sqrt{2}$. A point $v=(x,y)$ is chosen uniformly at random over all pairs of real numbers $x$ and $y$ such that $0 \le x \le 5000$ and $0 \le y \le 5000$. Let $T(v)$ be a translated copy of $S$ centered at $v$. What is the probability that the square region determ...
\frac{4}{625}
178
9
math
Given two linear functions \( f(x) \) and \( g(x) \) such that the graphs \( y=f(x) \) and \( y=g(x) \) are parallel lines, but not parallel to the coordinate axes. Find the minimum value of the function \( (g(x))^2 - 3f(x) \), if the minimum value of the function \( (f(x))^2 - 3g(x) \) is \( \frac{11}{2} \).
-10
102
3
math
Given the circle $(x+1)^2+y^2=2$, determine the center and radius of the circle.
(-1,0), \sqrt{2}
24
10
math
Automobile license plates for a region consist of four letters followed by a dash and three single digits. How many different license plate combinations are possible if exactly two letters are repeated once each, and digits increase consecutively?
15,600
44
6
math
Given that line $l$ passes through point $P(2, 1)$ with an inclination angle of $135^\circ$, establish a polar coordinate system with the origin $O$ as the pole and the positive semi-axis of $x$ as the polar axis (the unit length is consistent with that of the rectangular coordinate system $xoy$). The equation of circl...
\sqrt{14}
148
6
math
Given that the lines $y=k_{1}x$ and $y=k_{2}x(k_{1} > k_{2})$ are two tangent lines of the curve $y=ax+2\ln |x|$, calculate $k_{1}-k_{2}$.
\frac{4}{e}
59
7
math
Let $p$, $q$, and $r$ be the roots of $x^3 - 2x^2 - x + 3 = 0$. Find $\frac{1}{p-2} + \frac{1}{q-2} + \frac{1}{r-2}$.
-3
65
2
math
Given the three vertices of triangle $\triangle ABC$ are $A(1,4)$, $B(-2,3)$, and $C(4,-5)$, find the equation of the circumscribed circle, the coordinates of the circumcenter, and the radius of the circumscribed circle.
5
63
1
math
If each of the variables represents a different digit, what is the value of $a+b+c+d$? [asy] label("$a$",(1,0),E); label("$b$",(2,0),E); label("$c$",(3,0),E); label("$d$",(1,-1),E); label("$c$",(2,-1),E); label("$a$",(3,-1),E); label("+",(-2,-1),E); draw((-2.1,-1.4)--(4.1,-1.4),linewidth(0.5)); label("1",(0,-2),E); fo...
18
166
2
math
Given sets $A=\{x|1\leqslant x \lt 5\}$, $B=\{x|-a \lt x\leqslant a+3\}$. If $B\subseteq \left(A\cap B\right)$, determine the range of the real number $a$.
(-\infty, -1]
68
8
math
Given $f(x) = x^2 - 2017x + 8052 + |x^2 - 2017x + 8052|$, then find the value of $f(1) + f(2) + f(3) + \ldots + f(2013)$.
0
75
1
math
Given that $x > 2$, $y > 0$ and they satisfy $2^{x \cdot 2^{y}} = 16$, determine the minimum value of $\frac {2}{x-2} + \frac {2}{y}$.
4
56
1
math
Find the expected value and the variance of a random variable \(X\), which is uniformly distributed in the interval \([a ; b]\).
\mathrm{Var}(X) = \frac{(b - a)^2}{12}
29
20
math
Given that the line $l_{1}$: $x-3y+2=0$ is symmetric to the line $l_{2}$: $mx-y+b=0$ with respect to the $x$-axis, calculate the value of $m+b$.
-1
56
2
math
Find the matrix \(\mathbf{N}\) with real entries such that: \[ \mathbf{N}^2 - 3\mathbf{N} + 2\mathbf{N} = \begin{pmatrix} 6 & 12 \\ 3 & 6 \end{pmatrix}. \]
\begin{pmatrix} 2 & 4 \\ 1 & 2 \end{pmatrix}
72
23
math
Each of the eight letters in "GEOMETRY" is written on its own square tile and placed in a bag. What is the probability that a tile randomly selected from the bag will have a letter on it that is in the word "ANGLE"? Express your answer as a common fraction.
\frac{1}{4}
57
7
math
The inscribed circle of triangle $ABC$ is tangent to $\overline{AB}$ at $P,$ and its radius is $21$. Given that $AP=23$ and $PB=27,$ find the perimeter of the triangle.
345
52
3
math
A line with a slope of $-1$ is drawn through the right vertex $A$ of the hyperbola $\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1$ ($a > 0, b > 0$). This line intersects the two asymptotes of the hyperbola at points $B$ and $C$. If $2\overrightarrow{AB} = \overrightarrow{BC}$, then the eccentricity of the hyperbola is \_\_\_\_...
\sqrt{5}
117
5
math
If two numbers are randomly chosen without replacement from $\{2, 4, 6, 8\}$, what is the probability that their product will be a multiple of 8? Express your answer as a common fraction.
\frac{2}{3}
47
7
math
Randomly select 10 students from classes A and B of a certain school and measure their heights (unit: cm). The height data obtained are as follows: Class A: $170\ \ 179\ \ 162\ \ 168\ \ 158\ \ 182\ \ 179\ \ 168\ \ 163\ \ 171$ Class B: $159\ \ 173\ \ 179\ \ 178\ \ 162\ \ 181\ \ 176\ \ 168\ \ 170\ \ 165$ $(1)$ Calc...
165\ \text{cm}
191
9
math
A store received shipments of physics and mathematics textbooks. After selling $50\%$ of the mathematics textbooks and $20\%$ of the physics textbooks, totaling 390 books, the remaining number of mathematics textbooks was three times the number of remaining physics textbooks. How many mathematics and physics textbooks ...
720\text{ and } 150
69
12
math
Given a number is called flippy if its digits alternate between two distinct digits from the set {4, 6}, calculate the number of four-digit flippy numbers that are divisible by 4.
1
40
1
math
Given in $\triangle ABC$, $a$, $b$, $c$ are the sides opposite to angles $A$, $B$, $C$ respectively, satisfying $(5a-3b)\cos C=3c\cdot\cos B$. (Ⅰ) Find $\cos C$; (Ⅱ) If $c=4$, when the area of triangle $ABC$ is maximized, find the values of $a$ and $b$.
2\sqrt{5}
95
6
math
Diane has one 1-cent stamp, two identical 2-cent stamps, three identical 3-cent stamps, four identical 4-cent stamps, and five identical 5-cent stamps. How many different arrangements can Diane paste exactly 15 cents worth of postage in a row across the top of an envelope, given that she must use at least one of each s...
120
82
3
math
In the tetrahedron \(ABCD\), the ratios of the lengths are: \[ BD : CD : AB : AC : AD : BC = \sqrt{3} : \sqrt{2} : 1 : 1 : 1 : 1 \] Find the angle between \(AD\) and \(BC\).
60^\circ
68
4
math
A rectangle has a perimeter of 40 units, and one side is at least 3 units longer than the other side. Both dimensions are whole numbers. What is the maximum possible area of this rectangle in square units?
91
45
2
math
If \((2 x+4)^{2 n}=a_{0}+a_{1} x+a_{2} x^{2}+\cdots+a_{2 n} x^{2 n}\) for \(n \in \mathbf{N}^{+}\), then the remainder when \(a_{2}+a_{4}+\cdots+a_{2 n}\) is divided by 3 is .
1
89
1
math
Given the parabola $y^{2}=8x$ whose directrix intersects with the hyperbola $\dfrac {x^{2}}{a^{2}}- \dfrac {y^{2}}{b^{2}}=1$ ($a > 0,b > 0$) at points $A$ and $B$, and one of the asymptotes of the hyperbola is $y= \dfrac {4 \sqrt {3}}{3}x$, find the standard equation of the hyperbola.
\dfrac {x^{2}}{3}- \dfrac {y^{2}}{16}=1
112
23
math
Given that the value of $\pi = 3.1415926\ldots$, the largest integer not greater than $\pi^3$ is ____. The smallest integer not less than $\pi^3$ is ____.
32
50
2
math
A single bench section at a school event can hold either $7$ adults or $11$ children. When $N$ bench sections are connected end to end, an equal number of adults and children seated together will occupy all the bench space. What is the least possible positive integer value of $N?$
77
62
2
math
A right circular cylinder with its diameter equal to its height is inscribed in a right circular cone. The cone has a diameter of 18 and an altitude of 20. The axes of the cylinder and the cone coincide. Find the radius of the cylinder. Express your answer as a common fraction.
\frac{90}{19}
62
9
math
Let's say you deposit $X$ in a special savings account that initially increases your deposit by $r\%$ but then charges a management fee of $s\%$ on the new total. Find the condition on $r$ and $s$ such that the value of the deposit after these operations is still greater than $X$, given that $s < 20$. A) $r < \frac{100...
r > \frac{100s}{100 - s}
157
16
math
To the eight-digit number 20192020, prepend and append one digit each so that the resulting ten-digit number is divisible by 72. Indicate all possible solutions.
2201920200 \text{ and } 3201920208
41
26
math
Let $A$ denote the set of all integers $n$ such that $1 \le n \le 10000$ , and moreover the sum of the decimal digits of $n$ is $2$ . Find the sum of the squares of the elements of $A$ .
7294927
70
7
math
From this infinite list of numbers, how many are integers? $$\sqrt{6561},\sqrt[3]{6561},\sqrt[4]{6561},\sqrt[5]{6561},\sqrt[6]{6561},\ldots$$
3
65
1
math
Given that $f(x)$ is an odd function defined on $\mathbb{R}$, and $f(x+2)+f(x)=0$. When $x \in [0,1]$, $f(x)=2^x-1$. Find the value of $f(\log_{\frac{1}{8}}125)$.
\frac{1}{4}
73
7
math
In the process of selecting test points using the 0.618 method, if the experimental interval is $[1000,2000]$, and the first three test points are $x_1, x_2, x_3$ (with $x_2 < x_1$); and if the result at $x_2$ is better than that at $x_1$, then $x_3$ equals?
1236
95
4
math
A cylindrical soup can with a radius of 5 cm and a height of 10 cm is cut into a quarter wedge along its height by a planar cut through its axis. Calculate the volume of this quarter wedge.
196.25
45
6
math
The negation of the proposition "For all $x$ in $[1, 2]$, $x^2 < 4$" is.
\exists x \in [1, 2], x^2 \geq 4
31
19
math
How many tetrahedrons can be formed by choosing four vertices from the six vertices of a triangular prism?
12
22
2
math
The sides $a$, $b$, and $c$ of a triangle $\triangle ABC$ are opposite to angles $A$, $B$, and $C$, respectively. Given that $a+c=4$, and $\sin A (1+\cos B) = (2-\cos A)\sin B$, find the maximum area of $\triangle ABC$.
\sqrt{3}
73
5
math
Let $Q$ be the set of rational numbers, and $Z$ be the set of integers. In the coordinate plane, for a positive integer $m$, define the set of points $$ A_{m}=\left\{(x, y) \mid x, y \in \mathbf{Q}, x y \neq 0, \frac{x y}{m} \in \mathbf{Z}\right\}. $$ For a line segment $MN$, define $f_{m}(MN)$ as the number of points...
\lambda = 2
215
5
math
Given that $P(A)=0.7, P(B)=0.2, P(C)=0.1$, calculate the probability of the event "the drawn product is not a first-class product".
0.3
41
3
math
Given that points $F_1$ and $F_2$ are the left and right foci of the ellipse $\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$ $(a > b > 0)$, respectively, a line passing through $F_1$ perpendicular to the $x$-axis intersects the ellipse at points $A$ and $B$. If $\triangle ABF_2$ is an acute triangle, determine the range of the...
(\sqrt{2}-1, 1)
117
10
math
Selected Exercise $4-4$: Coordinate Systems and Parametric Equations In a rectangular coordinate system, a polar coordinate system is established with the origin as the pole and the positive half of the $x$-axis as the polar axis. The polar equation of curve $C$ is given by $\rho \sin^{2}\theta = 2a\cos\theta, (a > 0)...
a=1
226
3