olymmath

AIME 2002a

American Invitational Mathematics Examination 2002.

Paper

Problem 1

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Many states use a sequence of three letters followed by a sequence of three digits as their standard license-plate pattern. Given that each three-letter three-digit arrangement is equally likely, the probability that such a license plate will contain at least one palindrome (a three-letter arrangement or a three-digit arrangement that reads the same left-to-right as it does right-to-left) is mn\dfrac{m}{n}, where mm and nn are relatively prime positive integers. Find m+n.m+n.

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Problem 2

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The diagram shows twenty congruent circles arranged in three rows and enclosed in a rectangle. The circles are tangent to one another and to the sides of the rectangle as shown in the diagram. The ratio of the longer dimension of the rectangle to the shorter dimension can be written as 12(p−q)\dfrac{1}{2}(\sqrt{p}-q) where pp and qq are positive integers. Find p+qp+q.

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Problem 3

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Jane is 25 years old. Dick is older than Jane. In nn years, where nn is a positive integer, Dick's age and Jane's age will both be two-digit numbers and will have the property that Jane's age is obtained by interchanging the digits of Dick's age. Let dd be Dick's present age. How many ordered pairs of positive integers (d,n)(d,n) are possible?

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Problem 4

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Consider the sequence defined by ak=1k2+ka_k =\dfrac{1}{k^2+k} for k≥1k\geq 1. Given that am+am+1+⋯+an−1=129a_m+a_{m+1}+\cdots+a_{n-1}=\dfrac{1}{29}, for positive integers mm and nn with m<nm<n, find m+nm+n.

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Problem 5

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Let A1,A2,A3,⋯ ,A12A_1,A_2,A_3,\cdots,A_{12} be the vertices of a regular dodecagon. How many distinct squares in the plane of the dodecagon have at least two vertices in the set {A1,A2,A3,⋯ ,A12}?\{A_1,A_2,A_3,\cdots,A_{12}\} ?

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Problem 6

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The solutions to the system of equations are (x1,y1)(x_1,y_1) and (x2,y2)(x_2,y_2). Find log⁡30(x1y1x2y2)\log_{30}\left(x_1y_1x_2y_2\right).

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Problem 7

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The Binomial Expansion is valid for exponents that are not integers. That is, for all real numbers x,yx,y and rr with ∣x∣>∣y∣|x|>|y|, (x+y)r=xr+rxr−1y+r(r−1)2xr−2y2+r(r−1)(r−2)3!xr−3y3⋯(x+y)^r=x^r+rx^{r-1}y+\dfrac{r(r-1)}{2}x^{r-2}y^2+\dfrac{r(r-1)(r-2)}{3!}x^{r-3}y^3 \cdots What are the first three digits to the right of the decimal point in the decimal representation of (102002+1)107(10^{2002}+1)^{\frac{10}{7}}?

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Problem 8

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Find the smallest integer kk for which the conditions (1) a1,a2,a3⋯a_1,a_2,a_3\cdots is a nondecreasing sequence of positive integers (2) an=an−1+an−2a_n=a_{n-1}+a_{n-2} for all n>2n>2 (3) a9=ka_9=k are satisfied by more than one sequence.

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Problem 9

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Harold, Tanya, and Ulysses paint a very long picket fence. Call the positive integer 100h+10t+u100h+10t+u paintable when the triple (h,t,u)(h,t,u) of positive integers results in every picket being painted exactly once. Find the sum of all the paintable integers.

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Problem 10

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In the diagram below, angle ABCABC is a right angle. Point DD is on BC‾\overline{BC}, and AD‾\overline{AD} bisects angle CABCAB. Points EE and FF are on AB‾\overline{AB} and AC‾\overline{AC}, respectively, so that AE=3AE=3 and AF=10AF=10. Given that EB=9EB=9 and FC=27FC=27, find the integer closest to the area of quadrilateral DCFGDCFG.

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Problem 11

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Let ABCDABCD and BCFGBCFG be two faces of a cube with AB=12AB=12. A beam of light emanates from vertex AA and reflects off face BCFGBCFG at point PP, which is 7 units from BG‾\overline{BG} and 5 units from BC‾\overline{BC}. The beam continues to be reflected off the faces of the cube. The length of the light path from the time it leaves point AA until it next reaches a vertex of the cube is given by mnm\sqrt{n}, where mm and nn are integers and nn is not divisible by the square of any prime. Find m+nm+n.

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Problem 12

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Let F(z)=z+iz−iF(z)=\dfrac{z+i}{z-i} for all complex numbers z≠iz\neq i, and let zn=F(zn−1)z_n=F(z_{n-1}) for all positive integers nn. Given that z0=1137+iz_0=\dfrac{1}{137}+i and z2002=a+biz_{2002}=a+bi, where aa and bb are real numbers, find a+ba+b.

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Problem 13

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In triangle ABCABC the medians AD‾\overline{AD} and CE‾\overline{CE} have lengths 1818 and 2727, respectively, and AB=24AB=24. Extend CE‾\overline{CE} to intersect the circumcircle of ABCABC at FF. The area of triangle AFBAFB is mnm\sqrt{n}, where mm and nn are positive integers and nn is not divisible by the square of any prime. Find m+nm+n.

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Problem 14

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A set S\mathcal{S} of distinct positive integers has the following property: for every integer xx in S,\mathcal{S}, the arithmetic mean of the set of values obtained by deleting xx from S\mathcal{S} is an integer. Given that 1 belongs to S\mathcal{S} and that 2002 is the largest element of S,\mathcal{S}, what is the greatest number of elements that S\mathcal{S} can have?

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Problem 15

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Polyhedron ABCDEFGABCDEFG has six faces. Face ABCDABCD is a square with AB=12;AB = 12; face ABFGABFG is a trapezoid with AB‾\overline{AB} parallel to GF‾,\overline{GF}, BF=AG=8,BF = AG = 8, and GF=6;GF = 6; and face CDECDE has CE=DE=14.CE = DE = 14. The other three faces are ADEG,BCEF,ADEG, BCEF, and EFG.EFG. The distance from EE to face ABCDABCD is 12. Given that EG2=p−qr,EG^2 = p - q\sqrt {r}, where p,q,p, q, and rr are positive integers and rr is not divisible by the square of any prime, find p+q+r.p + q + r.

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