olymmath

AIME 2023b

American Invitational Mathematics Examination 2023.

Paper

Problem 1

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The numbers of apples growing on each of six apple trees form an arithmetic sequence where the greatest number of apples growing on any of the six trees is double the least number of apples growing on any of the six trees. The total number of apples growing on all six trees is 990.990. Find the greatest number of apples growing on any of the six trees.

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Problem 2

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Recall that a palindrome is a number that reads the same forward and backward. Find the greatest integer less than 10001000 that is a palindrome both when written in base ten and when written in base eight, such as 292=4448.292 = 444_{8}.

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Problem 3

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Let △ABC\triangle ABC be an isosceles triangle with ∠A=90∘.\angle A = 90^\circ. There exists a point PP inside △ABC\triangle ABC such that ∠PAB=∠PBC=∠PCA\angle PAB = \angle PBC = \angle PCA and AP=10.AP = 10. Find the area of △ABC.\triangle ABC.

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Problem 4

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Let x,y,x,y, and zz be real numbers satisfying the system of equations \begin{align*} xy + 4z &= 60 \ yz + 4x &= 60 \ zx + 4y &= 60. \end{align*} Let SS be the set of possible values of x.x. Find the sum of the squares of the elements of S.S.

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Problem 5

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Let SS be the set of all positive rational numbers rr such that when the two numbers rr and 55r55r are written as fractions in lowest terms, the sum of the numerator and denominator of one fraction is the same as the sum of the numerator and denominator of the other fraction. The sum of all the elements of SS can be expressed in the form pq,\frac{p}{q}, where pp and qq are relatively prime positive integers. Find p+q.p+q.

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Problem 6

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Consider the L-shaped region formed by three unit squares joined at their sides, as shown below. Two points AA and BB are chosen independently and uniformly at random from inside the region. The probability that the midpoint of AB‾\overline{AB} also lies inside this L-shaped region can be expressed as mn,\frac{m}{n}, where mm and nn are relatively prime positive integers. Find m+n.m+n. [asy] unitsize(2cm); draw((0,0)--(2,0)--(2,1)--(1,1)--(1,2)--(0,2)--cycle); draw((0,1)--(1,1)--(1,0),dashed); [/asy]

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Problem 7

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Each vertex of a regular dodecagon (1212-gon) is to be colored either red or blue, and thus there are 2122^{12} possible colorings. Find the number of these colorings with the property that no four vertices colored the same color are the four vertices of a rectangle.

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Problem 8

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Let ω=cos⁡2π7+i⋅sin⁡2π7,\omega = \cos\frac{2\pi}{7} + i \cdot \sin\frac{2\pi}{7}, where i=−1.i = \sqrt{-1}. Find the value of the product∏k=06(ω3k+ωk+1).\prod_{k=0}^6 \left(\omega^{3k} + \omega^k + 1\right).

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Problem 9

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Circles ω1\omega_1 and ω2\omega_2 intersect at two points PP and Q,Q, and their common tangent line closer to PP intersects ω1\omega_1 and ω2\omega_2 at points AA and B,B, respectively. The line parallel to ABAB that passes through PP intersects ω1\omega_1 and ω2\omega_2 for the second time at points XX and Y,Y, respectively. Suppose PX=10,PX=10, PY=14,PY=14, and PQ=5.PQ=5. Then the area of trapezoid XABYXABY is mn,m\sqrt{n}, where mm and nn are positive integers and nn is not divisible by the square of any prime. Find m+n.m+n.

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Problem 10

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Let NN be the number of ways to place the integers 11 through 1212 in the 1212 cells of a 2×62 \times 6 grid so that for any two cells sharing a side, the difference between the numbers in those cells is not divisible by 3.3. One way to do this is shown below. Find the number of positive integer divisors of N.N. 135791124681012\begin{array}{|c|c|c|c|c|c|} \hline 1 & 3 & 5 & 7 & 9 & 11 \\ \hline 2 & 4 & 6 & 8 & 10 & 12 \\ \hline \end{array}

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Problem 11

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Find the number of collections of 1616 distinct subsets of {1,2,3,4,5}\{1,2,3,4,5\} with the property that for any two subsets XX and YY in the collection, X∩Y≠∅.X \cap Y \not= \emptyset.

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Problem 12

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In △ABC\triangle ABC with side lengths AB=13,AB = 13, BC=14,BC = 14, and CA=15,CA = 15, let MM be the midpoint of BC‾.\overline{BC}. Let PP be the point on the circumcircle of △ABC\triangle ABC such that MM is on AP‾.\overline{AP}. There exists a unique point QQ on segment AM‾\overline{AM} such that ∠PBQ=∠PCQ.\angle PBQ = \angle PCQ. Then AQAQ can be written as mn,\frac{m}{\sqrt{n}}, where mm and nn are relatively prime positive integers. Find m+n.m+n.

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Problem 13

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Let AA be an acute angle such that tan⁡A=2cos⁡A.\tan A = 2 \cos A. Find the number of positive integers nn less than or equal to 10001000 such that sec⁡nA+tan⁡nA\sec^n A + \tan^n A is a positive integer whose units digit is 9.9.

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Problem 14

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A cube-shaped container has vertices A,A, B,B, C,C, and D,D, where AB‾\overline{AB} and CD‾\overline{CD} are parallel edges of the cube, and AC‾\overline{AC} and BD‾\overline{BD} are diagonals of faces of the cube, as shown. Vertex AA of the cube is set on a horizontal plane P\mathcal{P} so that the plane of the rectangle ABDCABDC is perpendicular to P,\mathcal{P}, vertex BB is 22 meters above P,\mathcal{P}, vertex CC is 88 meters above P,\mathcal{P}, and vertex DD is 1010 meters above P.\mathcal{P}. The cube contains water whose surface is parallel to P\mathcal{P} at a height of 77 meters above P.\mathcal{P}. The volume of water is mn\frac{m}{n} cubic meters, where mm and nn are relatively prime positive integers. Find m+n.m+n.

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Problem 15

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For each positive integer nn let ana_n be the least positive integer multiple of 2323 such that an≡1(mod2n).a_n \equiv 1 \pmod{2^n}. Find the number of positive integers nn less than or equal to 10001000 that satisfy an=an+1.a_n = a_{n+1}.

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