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40.3k
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100
16,000
Determine the value of the following expression: $$ \left\lfloor\frac{11}{2010}\right\rfloor+\left\lfloor\frac{11 \times 2}{2010}\right\rfloor+\left\lfloor\frac{11 \times 3}{2010}\right\rfloor+\\left\lfloor\frac{11 \times 4}{2010}\right\rfloor+\cdots+\left\lfloor\frac{11 \times 2009}{2010}\right\rfloor, $$ where \(\lfl...
10045
86.71875
16,001
Square \(ABCD\) has side length 2, and \(X\) is a point outside the square such that \(AX = XB = \sqrt{2}\). What is the length of the longest diagonal of pentagon \(AXB\)?
\sqrt{10}
14.84375
16,002
In the expression \((x+y+z)^{2030}+(x-y-z)^{2030}\), the parentheses were expanded, and like terms were collected. How many monomials of the form \(x^{a} y^{b} z^{c}\) have a nonzero coefficient?
1032256
41.40625
16,003
The brakes of a car allow it to stay stationary on an inclined asphalt surface with a base angle not exceeding $30^{\circ}$. Determine the minimum braking distance of this car when traveling at a speed of $30 \, \text{m/s}$ on a flat horizontal road with the same surface. The acceleration due to gravity is $g=10 \, \te...
78
6.25
16,004
27 identical dice were glued together to form a $3 \times 3 \times 3$ cube in such a way that any two adjacent small dice have the same number of dots on the touching faces. How many dots are there on the surface of the large cube?
189
17.96875
16,005
Find the smallest positive integer $n$ that satisfies the following conditions: For $n$, there exists a positive integer $k$ such that $\frac{8}{15} < \frac{n}{n+k} < \frac{7}{13}$.
15
0.78125
16,006
Two circles are externally tangent to each other at point \( A \), and both are tangent to a third circle at points \( B \) and \( C \). The extension of chord \( AB \) of the first circle intersects the second circle at point \( D \), and the extension of chord \( AC \) intersects the first circle at point \( E \). Th...
13
1.5625
16,007
A number of trucks with the same capacity were requested to transport cargo from one place to another. Due to road issues, each truck had to carry 0.5 tons less than planned, which required 4 additional trucks. The mass of the transported cargo was at least 55 tons but did not exceed 64 tons. How many tons of cargo wer...
2.5
35.9375
16,008
Someone forms an integer by writing the integers from 1 to 82 in ascending order, i.e. 1234567891011 ...808182. Find the sum of the digits of this integer.
667
34.375
16,009
Given a polygon drawn on graph paper with a perimeter of 2014 units, and whose sides follow the grid lines, what is the maximum possible area of this polygon?
253512
16.40625
16,010
Into each row of a \( 9 \times 9 \) grid, Nigel writes the digits \( 1, 2, 3, 4, 5, 6, 7, 8, 9 \) in order, starting at one of the digits and returning to 1 after 9: for example, one row might contain \( 7, 8, 9, 1, 2, 3, 4, 5, 6 \). The grid is gorgeous if each nine-digit number read along a row or column or along the...
9^8
0
16,011
On the hypotenuse \( AB \) of a right triangle \( ABC \), square \( ABDE \) is constructed externally with \( AC=2 \) and \( BC=5 \). In what ratio does the angle bisector of angle \( C \) divide side \( DE \)?
2 : 5
33.59375
16,012
Find the number of the form $7x36y5$ that is divisible by 1375.
713625
35.9375
16,013
Given a tetrahedron \(ABCD\). Points \(M\), \(N\), and \(K\) lie on edges \(AD\), \(BC\), and \(DC\) respectively, such that \(AM:MD = 1:3\), \(BN:NC = 1:1\), and \(CK:KD = 1:2\). Construct the section of the tetrahedron with the plane \(MNK\). In what ratio does this plane divide the edge \(AB\)?
2/3
0.78125
16,014
Three friends are driving cars on a road in the same direction. At a certain moment, they are positioned relative to each other as follows: Andrews is at a certain distance behind Brooks, and Carter is at a distance twice the distance from Andrews to Brooks, ahead of Brooks. Each driver is traveling at a constant speed...
6.666666666666667
0
16,015
Given is a regular tetrahedron of volume 1. We obtain a second regular tetrahedron by reflecting the given one through its center. What is the volume of their intersection?
\frac{1}{2}
60.15625
16,016
What fraction of the volume of a parallelepiped is the volume of a tetrahedron whose vertices are the centroids of the tetrahedra cut off by the planes of a tetrahedron inscribed in the parallelepiped?
1/24
0.78125
16,017
Given that points $\mathbf{A}$ and $\mathbf{B}$ lie on the curves $C_{1}: x^{2} - y + 1 = 0$ and $C_{2}: y^{2} - x + 1 = 0$ respectively, determine the minimum value of $|AB|$.
\frac{3 \sqrt{2}}{4}
76.5625
16,018
Mice built an underground house consisting of chambers and tunnels: - Each tunnel leads from one chamber to another (i.e., none are dead ends). - From each chamber, exactly three tunnels lead to three different chambers. - From each chamber, it is possible to reach any other chamber through tunnels. - There is exactly...
10
13.28125
16,019
Every second, the computer displays a number equal to the sum of the digits of the previous number multiplied by 31. On the first second, the number 2020 was displayed. What number will be displayed on the screen on the 2020th second?
310
10.9375
16,020
In the center of a circular field stands a geologists' house. From it, 8 straight roads extend, dividing the field into 8 equal sectors. Two geologists embark on a journey from their house at a speed of 5 km/h, each choosing a road at random. Determine the probability that the distance between them will be more than 8 ...
0.375
0
16,021
Given a triangular pyramid \( S-ABC \) with vertex \( S \). The projection of \( S \) onto the base \( \triangle ABC \) is the orthocenter \( H \) of \( \triangle ABC \). Additionally, \( BC = 2 \), \( SB = SC \), and the dihedral angle between the face \( SBC \) and the base is \( 60^\circ \). Determine the volume of ...
\frac{\sqrt{3}}{3}
21.09375
16,022
In a box, there are 100 balls of different colors: 28 red balls, 20 green balls, 12 yellow balls, 20 blue balls, 10 white balls, and 10 black balls. How many balls must be drawn randomly from the box to ensure that at least 15 of them are of the same color?
75
78.90625
16,023
The regular hexagon \(ABCDEF\) has diagonals \(AC\) and \(CE\). The internal points \(M\) and \(N\) divide these diagonals such that \(AM: AC = CN: CE = r\). Determine \(r\) if it is known that points \(B\), \(M\), and \(N\) are collinear.
\frac{1}{\sqrt{3}}
0.78125
16,024
Given four points \(O, A, B, C\) on a plane, such that \(OA = 4\), \(OB = 3\), \(OC = 2\), and \(\overrightarrow{OB} \cdot \overrightarrow{OC} = 3\), find the maximum value of the area \(S_{\triangle ABC}\).
2\sqrt{7} + \frac{3\sqrt{3}}{2}
0
16,025
Find the number of ways to pave a $1 \times 10$ block with tiles of sizes $1 \times 1, 1 \times 2$ and $1 \times 4$, assuming tiles of the same size are indistinguishable. It is not necessary to use all the three kinds of tiles.
169
86.71875
16,026
Two digits of a number were swapped, and as a result, it increased by more than 3 times. The resulting number is 8453719. Find the original number.
1453789
14.84375
16,027
In quadrilateral \(ABCD\), \(\angle DAC = 98^\circ\), \(\angle DBC = 82^\circ\), \(\angle BCD = 70^\circ\), and \(BC = AD\). Find \(\angle ACD\).
28
21.875
16,028
Inside the cube \(ABCD A_{1}B_{1}C_{1}D_{1}\) there is a sphere with center \(O\) and radius 10. The sphere intersects the face \(AA_{1}D_{1}D\) in a circle of radius 1, the face \(A_{1}B_{1}C_{1}D_{1}\) in a circle of radius 1, and the face \(CD D_{1}C_{1}\) in a circle of radius 3. Find the length of the segment \(OD...
17
30.46875
16,029
There are 100 chairs arranged in a circle. If \( n \) people are sitting on these chairs, such that any new person sitting down will always sit on a chair adjacent to one of the \( n \) people, what is the minimum value of \( n \)?
34
72.65625
16,030
Calculate the definite integral: $$ \int_{0}^{\frac{\pi}{2}} \frac{\sin x \, dx}{(1+\sin x)^{2}} $$
\frac{1}{3}
19.53125
16,031
In triangle \( ABC \), let \( E \) be the point where the side \( AC \) is divided into quarters closest to \( C \), and let \( F \) be the midpoint of side \( BC \). The line passing through points \( E \) and \( F \) intersects line \( AB \) at point \( D \). What percentage of the area of triangle \( ABC \) is the a...
112.5
26.5625
16,032
Given the sets \( M=\{x, xy, \lg(xy)\} \) and \( N=\{0, |x|, y\} \), and that \( M=N \), find the value of \( \left(x+\frac{1}{y}\right)+\left(x^{2}+\frac{1}{y^{2}}\right)+\left(x^{3}+\frac{1}{y^{3}}\right)+\cdots+\left(x^{2001}+\frac{1}{y^{2001}}\right) \).
-2
24.21875
16,033
Let $L$ be the intersection point of the diagonals $CE$ and $DF$ of a regular hexagon $ABCDEF$ with side length 2. Point $K$ is defined such that $\overrightarrow{LK} = \overrightarrow{AC} - 3 \overrightarrow{BC}$. Determine whether point $K$ lies inside, on the boundary, or outside of $ABCDEF$, and find the length of ...
\frac{2\sqrt{3}}{3}
6.25
16,034
Find the number of 2's in the factorization of the number $2011 \cdot 2012 \cdot 2013 \cdot \ldots \cdot 4020$. Provide the answer in the given field.
2010
44.53125
16,035
The bases \(AB\) and \(CD\) of the trapezoid \(ABCD\) are 41 and 24 respectively, and its diagonals are mutually perpendicular. Find the dot product of the vectors \(\overrightarrow{AD}\) and \(\overrightarrow{BC}\).
984
50.78125
16,036
Find the minimum value for \(a, b > 0\) of the expression $$ \frac{|2a - b + 2a(b - a)| + |b + 2a - a(b + 4a)|}{\sqrt{4a^2 + b^2}} $$
\frac{\sqrt{5}}{5}
6.25
16,037
In \( \triangle ABC \), \( AB = 4 \), \( BC = 7 \), \( CA = 5 \). Let \(\angle BAC = \alpha\). Find the value of \( \sin^6 \frac{\alpha}{2} + \cos^6 \frac{\alpha}{2} \).
7/25
83.59375
16,038
If a positive integer has eight positive divisors and the sum of these eight positive divisors is 3240, it is called a "good number." For example, 2006 is a good number because the sum of its positive divisors $1, 2, 17, 34, 59, 118, 1003, 2006$ is 3240. Find the smallest good number.
1614
31.25
16,039
For a natural number \( N \), if at least eight out of the nine natural numbers from 1 to 9 can divide \( N \), then \( N \) is called a "Ba Xian number". What is the smallest "Ba Xian number" greater than 2000?
2016
91.40625
16,040
There are exactly 120 ways to color five cells in a \( 5 \times 5 \) grid such that each row and each column contains exactly one colored cell. There are exactly 96 ways to color five cells in a \( 5 \times 5 \) grid without the corner cell such that each row and each column contains exactly one colored cell. How man...
78
66.40625
16,041
In rectangle \(ABCD\), \(AB = 2\) and \(AD = 1\). Let \(P\) be a moving point on side \(DC\) (including points \(D\) and \(C\)), and \(Q\) be a moving point on the extension of \(CB\) (including point \(B\)). The points \(P\) and \(Q\) satisfy \(|\overrightarrow{DP}| = |\overrightarrow{BQ}|\). What is the minimum value...
3/4
68.75
16,042
The difference between the cube and the square of a number has the form $a b c a b c$ (in the decimal system). What is this number?
78
81.25
16,043
Calculate the volumes of the solids formed by rotating the regions bounded by the graphs of the functions around the y-axis. $$ y = \arcsin x, \quad y = \arccos x, \quad y = 0 $$
\frac{\pi}{2}
3.90625
16,044
An archipelago consists of $N \geqslant 7$ islands. Any two islands are connected by at most one bridge. It is known that no more than 5 bridges lead from each island, and among any 7 islands, there are always at least two connected by a bridge. What is the maximum possible value of $N$?
36
6.25
16,045
In trapezoid \(ABCD\) with \(BC \parallel AD\), it is known that \(AD = 3 \cdot BC\). A line intersects the non-parallel sides of the trapezoid at points \(M\) and \(N\) such that \(AM:MB = 3:5\) and \(CN:ND = 2:7\). Find the ratio of the areas of quadrilaterals \(MBCN\) and \(AMND\).
9/23
0
16,046
Given the sequence: $\frac{2}{3}, \frac{2}{9}, \frac{4}{9}, \frac{6}{9}, \frac{8}{9}, \frac{2}{27}, \frac{4}{27}, \cdots$, $\frac{26}{27}, \cdots, \frac{2}{3^{n}}, \frac{4}{3^{n}}, \cdots, \frac{3^{n}-1}{3^{n}}, \cdots$. Find the position of $\frac{2018}{2187}$ in the sequence.
1552
23.4375
16,047
Two right triangles \( \triangle AXY \) and \( \triangle BXY \) have a common hypotenuse \( XY \) and side lengths (in units) \( AX=5 \), \( AY=10 \), and \( BY=2 \). Sides \( AY \) and \( BX \) intersect at \( P \). Determine the area (in square units) of \( \triangle PXY \).
25/3
1.5625
16,048
Petya can draw only 4 things: a sun, a ball, a tomato, and a banana. Today he drew several things, including exactly 15 yellow items, 18 round items, and 13 edible items. What is the maximum number of balls he could have drawn? Petya believes that all tomatoes are round and red, all balls are round and can be of any c...
18
8.59375
16,049
Let \( f(x) = \left\{ \begin{array}{cc} 1 & 1 \leqslant x \leqslant 2 \\ x-1 & 2 < x \leqslant 3 \end{array} \right. \). For any \( a \,(a \in \mathbb{R}) \), define \( v(a) = \max \{ f(x) - a x \mid x \in [1,3] \} - \min \{ f(x) - a x \mid x \in [1,3] \} \). Draw the graph of \( v(a) \) and find the minimum value of \...
\frac{1}{2}
30.46875
16,050
Find the flux of the vector field \(\mathbf{a} = y^2 \mathbf{j} + z \mathbf{k}\) through the part of the surface \(z = x^2 + y^2\), cut off by the plane \(z=2\). The normal vector is taken to be outward with respect to the region bounded by the paraboloid.
-2\pi
27.34375
16,051
Find all integers \( n \) such that \( n^{4} + 6n^{3} + 11n^{2} + 3n + 31 \) is a perfect square.
10
88.28125
16,052
Let \( p(x) = x^{4} + a x^{3} + b x^{2} + c x + d \), where \( a, b, c, d \) are constants, and \( p(1) = 1993 \), \( p(2) = 3986 \), \( p(3) = 5979 \). Calculate \( \frac{1}{4}[p(11) + p(-7)] \).
5233
38.28125
16,053
A production team in a factory is manufacturing a batch of parts. Initially, when each worker is on their own original position, the task can be completed in 9 hours. If the positions of workers $A$ and $B$ are swapped, and other workers' efficiency remains the same, the task can be completed one hour earlier. Similarl...
108
7.8125
16,054
Someone wrote down two numbers $5^{2020}$ and $2^{2020}$ consecutively. How many digits will the resulting number contain?
2021
28.90625
16,055
In the number $2 * 0 * 1 * 6 * 0 * 2 *$, each of the 6 asterisks must be replaced with any of the digits $0, 2, 4, 5, 7, 9$ (digits may be repeated) so that the resulting 12-digit number is divisible by 12. How many ways can this be done?
5184
51.5625
16,056
The common ratio of the geometric sequence \( a+\log _{2} 3, a+\log _{1} 3, a+\log _{8} 3 \) is ______.
\frac{1}{3}
23.4375
16,057
Find the smallest positive integer \( m \) such that the equation regarding \( x, y, \) and \( z \): \[ 2^x + 3^y - 5^z = 2m \] has no positive integer solutions.
11
40.625
16,058
Let \( S = \{1, 2, 3, 4, \ldots, 50\} \). A 3-element subset \(\{a, b, c\}\) of \(S\) is said to be good if \(a + b + c\) is divisible by 3. Determine the number of 3-element subsets of \(S\) which are good.
6544
85.15625
16,059
In an isosceles trapezoid \(ABCD\), the larger base \(AD = 12\) and \(AB = 6\). Find the distance from point \(O\), the intersection of the diagonals, to point \(K\), the intersection of the extensions of the lateral sides, given that the extensions of the lateral sides intersect at a right angle.
\frac{12(3 - \sqrt{2})}{7}
0
16,060
Given a four-digit number $\overline{A B C D}$ that satisfies the following properties: $\overline{A B}$, $\overline{B C}$, and $\overline{C D}$ are all perfect squares (a perfect square is a number that can be expressed as the square of an integer, such as $4 = 2^2$ and $81 = 9^2$). What is the sum of all four-digit n...
13462
70.3125
16,061
What is the minimum number of points that can be chosen on a circle with a circumference of 1956 so that for each of these points there is exactly one chosen point at a distance of 1 and exactly one at a distance of 2 (distances are measured along the circle)?
1304
0.78125
16,062
Positive numbers \(a\), \(b\), and \(c\) satisfy the following equations: \[ a^{2} + a b + b^{2} = 1 \] \[ b^{2} + b c + c^{2} = 3 \] \[ c^{2} + c a + a^{2} = 4 \] Find \(a + b + c\).
\sqrt{7}
54.6875
16,063
For each positive integer $n$, an associated non-negative integer $f(n)$ is defined to satisfy the following three rules: i) $f(a b)=f(a)+f(b)$. ii) $f(n)=0$ if $n$ is a prime greater than 10. iii) $f(1)<f(243)<f(2)<11$. Given that $f(2106)<11$, determine the value of $f(96)$.
31
48.4375
16,064
There are two types of tables in a restaurant: a square table can seat 4 people, and a round table can seat 9 people. The restaurant manager calls a number a "wealth number" if the total number of diners can exactly fill a certain number of tables. How many "wealth numbers" are there among the numbers from 1 to 100?
88
100
16,065
The product of three consecutive even numbers has the form $87XXXXX8$. Provide the 5 missing digits. ($X$ does not necessarily represent the same digits.)
52660
7.8125
16,066
Given ten 0's and ten 1's, how many 0-1 binary sequences can be formed such that no three or more consecutive 0's are together? For example, 01001001010011101011 is such a sequence, but the sequence 01001000101001110111 does not satisfy this condition.
24068
47.65625
16,067
"Sun", "Xing", and "Zhe" each represent a digit. The product of the two three-digit numbers 'SunXingZhe' and 'ZheXingSun' is 78445. Can you find the sum of these two three-digit numbers?
686
10.9375
16,068
The kindergarten teacher evenly distributed 270 apples, 180 pears, and 235 oranges to the larger group of children. The remaining quantities of apples, pears, and oranges are in the ratio $3:2:1$. How many children are there in the larger group?
29
12.5
16,069
The equations of the sides of a quadrilateral are: $$ y=-x+7, \quad y=\frac{x}{2}+1, \quad y=-\frac{3}{2} x+2 \quad \text {and} \quad y=\frac{7}{4} x+\frac{3}{2}. $$ Determine the area of the quadrilateral.
\frac{327}{52}
7.03125
16,070
For the set \( \{x \mid a \leqslant x \leqslant b\} \), we define \( b-a \) as its length. Let the set \( A=\{x \mid a \leqslant x \leqslant a+1981\} \), \( B=\{x \mid b-1014 \leqslant x \leqslant b\} \), and both \( A \) and \( B \) are subsets of the set \( U=\{x \mid 0 \leqslant x \leqslant 2012\} \). The minimum le...
983
15.625
16,071
Investment funds A, B, and C claim that they can earn profits of 200%, 300%, and 500% respectively in one year. Tommy has $90,000 and plans to invest in these funds. However, he knows that only one of these funds can achieve its claim while the other two will close down. He has thought of an investment plan which can g...
30000
6.25
16,072
There are 2006 positive integers \( a_{1}, a_{2}, \cdots, a_{2006} \) (which can be the same) such that the ratios \( \frac{a_{1}}{a_{2}}, \frac{a_{2}}{a_{3}}, \cdots, \frac{a_{2005}}{a_{2006}} \) are all distinct. What is the minimum number of distinct numbers among \( a_{1}, a_{2}, \cdots, a_{2006} \)?
46
3.90625
16,073
In a scalene triangle with integer side lengths $a, b, c$, the following relation holds. What is the smallest height of the triangle? $$ \frac{a^{2}}{c}-(a-c)^{2}=\frac{b^{2}}{c}-(b-c)^{2} $$
2.4
1.5625
16,074
Let \(CD\) be a chord of a circle \(\Gamma_{1}\) and \(AB\) a diameter of \(\Gamma_{1}\) perpendicular to \(CD\) at \(N\) with \(AN > NB\). A circle \(\Gamma_{2}\) centered at \(C\) with radius \(CN\) intersects \(\Gamma_{1}\) at points \(P\) and \(Q\), and the segments \(PQ\) and \(CD\) intersect at \(M\). Given that ...
78
0
16,075
How many four-digit numbers can be formed using three 1s, two 2s, and five 3s?
71
14.84375
16,076
Define the lengths of intervals $(m, n)$, $[m, n)$, $(m, n]$, and $[m, n]$ to be $n - m$ ($n, m \in \mathbf{R}$ and $n > m$). Find the sum of the lengths of the intervals for real numbers $x$ that satisfy the inequality \[ \frac{1}{x-20}+\frac{1}{x-17} \geqslant \frac{1}{512} \]
1024
48.4375
16,077
It is given that \( a = 103 \times 97 \times 10009 \). Find \( a \).
99999919
97.65625
16,078
In a trapezoid, the lengths of the bases are 5 and 15, and the lengths of the diagonals are 12 and 16. Find the area of the trapezoid.
96
17.96875
16,079
Numbers $1,2,3,4,5,6,7,$ and $8$ are placed at the vertices of a cube such that the sum of any three numbers belonging to any face of the cube is not less than 10. Find the minimum possible sum of four numbers belonging to one face.
16
89.0625
16,080
In a $10 \times 5$ grid, an ant starts from point $A$ and can only move right or up along the grid lines but is not allowed to pass through point $C$. How many different paths are there from point $A$ to point $B$?
1827
20.3125
16,081
Two identical cylindrical vessels are connected at the bottom with a small-diameter tube with a valve. While the valve was closed, water was poured into the first vessel and oil was poured into the second vessel, so that the liquid levels were identical and equal to $h = 40 \text{ cm}$. At what level will the water est...
32.94
19.53125
16,082
In a taxi, a passenger can sit in the front and three passengers can sit in the back. In how many ways can four passengers sit in a taxi if one of these passengers wants to sit by the window?
18
60.15625
16,083
Determine the number $ABCC$ (written in decimal system) given that $$ ABCC = (DD - E) \cdot 100 + DD \cdot E $$ where $A, B, C, D,$ and $E$ are distinct digits.
1966
3.125
16,084
Twelve mayoral candidates each made a statement about how many times lies had been told before their turn. The first candidate said, "Before me, one lie was told." The second candidate said, "Now, two lies have been told." The third candidate said, "Now, three lies have been told," and so on, until the twelfth candidat...
11
34.375
16,085
Calculate the definite integral: $$ \int_{-1}^{0}(x+2)^{3} \cdot \ln ^{2}(x+2) \, dx $$
4 \ln^{2} 2 - 2 \ln 2 + \frac{15}{32}
0
16,086
Given the function \( f(n) \) defined on the set of natural numbers \(\mathbf{N}\), and satisfies: \[ \begin{array}{l} f(1) = f(2) = 1, \\ f(3n) = 3 f(n) - 2, \\ f(3n+1) = 3 f(n) + 1, \\ f(3n+2) = 3 f(n) + 4 \quad (n \in \mathbf{N}). \end{array} \] Determine the largest positive integer \( n \) less than or equal to ...
1093
100
16,087
Points \( M \) and \( N \) are located on side \( BC \) of triangle \( ABC \), and point \( K \) is on side \( AC \), with \( BM : MN : NC = 1 : 1 : 2 \) and \( CK : AK = 1 : 4 \). Given that the area of triangle \( ABC \) is 1, find the area of quadrilateral \( AMNK \).
13/20
1.5625
16,088
The real numbers \( x, y, z \) satisfy the equations \( x + y + z = 2 \) and \( xy + yz + zx = 1 \). Find the maximum possible value of \( x - y \).
\frac{2 \sqrt{3}}{3}
40.625
16,089
Subset \( S \subseteq \{1, 2, 3, \ldots, 1000\} \) is such that if \( m \) and \( n \) are distinct elements of \( S \), then \( m + n \) does not belong to \( S \). What is the largest possible number of elements in \( S \)?
501
6.25
16,090
In triangle \(ABC\), a point \(D\) is marked on side \(AC\) such that \(BC = CD\). Find \(AD\) if it is known that \(BD = 13\) and angle \(CAB\) is three times smaller than angle \(CBA\).
13
35.15625
16,091
Consider the permutation of $1, 2, \cdots, 20$ as $\left(a_{1} a_{2} \cdots a_{20}\right)$. Perform the following operation on this permutation: swap the positions of any two numbers. The goal is to transform this permutation into $(1, 2, \cdots, 20)$. Let $k_{a}$ denote the minimum number of operations needed to reach...
19
0.78125
16,092
Given that the volume of the tetrahedron \(ABCD\) is 40, \(AB = 7\), \(BC = 8\), \(AC = 9\), and the orthogonal projection of vertex \(D\) onto the plane \(ABC\) is precisely the incenter \(H\) of triangle \(ABC\), what is the surface area of the tetrahedron?
60 + 12 \sqrt{5}
0.78125
16,093
From the first 539 positive integers, we select some such that their sum is at least one-third of the sum of the original numbers. What is the minimum number of integers we need to select for this condition to be satisfied?
99
40.625
16,094
An elevator containing 9 passengers can stop at ten different floors. The passengers exit in groups of two, three, and four people. In how many ways can this happen?
10 * 9 * 8 * 36 * 35
0
16,095
A cashier, upon checking the account before leaving work, finds that the cash is 153 yuan less than the account book. She knows the actual amount collected cannot be wrong, so it must be due to a decimal point error during bookkeeping. What is the actual amount of the cash that was recorded incorrectly?
17
31.25
16,096
Each vertex of the parallelogram $ABCD$ lies on the same side of the plane $S$ such that the distances of the vertices $A, B$, and $C$ from the plane $S$ are 4 cm, 6 cm, and 8 cm, respectively. The area of the projection of the parallelogram onto the plane $S$, which forms the quadrilateral $A'B'C'D'$, is $10 \text{ cm...
60
54.6875
16,097
How many five-digit numbers are there that are divisible by 5 and do not contain repeating digits?
5712
28.125
16,098
From the 20 numbers 11, 12, 13, 14, ... 30, how many numbers must be chosen to ensure that there are at least two numbers whose sum is a multiple of 10?
11
39.0625
16,099
Cátia leaves school every day at the same time and rides her bicycle home. When she pedals at $20 \mathrm{~km} / \mathrm{h}$, she arrives home at $4:30$ PM. If she pedals at $10 \mathrm{~km} / \mathrm{h}$, she arrives home at $5:15$ PM. At what speed should she pedal to arrive home at $5:00$ PM?
12
22.65625