olymmath

AIME 2009b

American Invitational Mathematics Examination 2009.

Paper

Problem 1

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Before starting to paint, Bill had 130130 ounces of blue paint, 164164 ounces of red paint, and 188188 ounces of white paint. Bill painted four equally sized stripes on a wall, making a blue stripe, a red stripe, a white stripe, and a pink stripe. Pink is a mixture of red and white, not necessarily in equal amounts. When Bill finished, he had equal amounts of blue, red, and white paint left. Find the total number of ounces of paint Bill had left.

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Problem 2

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Suppose that aa, bb, and cc are positive real numbers such that alog⁡37=27a^{\log_3 7} = 27, blog⁡711=49b^{\log_7 11} = 49, and clog⁡1125=11c^{\log_{11}25} = \sqrt{11}. Find a(log⁡37)2+b(log⁡711)2+c(log⁡1125)2.a^{(\log_3 7)^2} + b^{(\log_7 11)^2} + c^{(\log_{11} 25)^2}.

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Problem 3

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In rectangle ABCDABCD, AB=100AB=100. Let EE be the midpoint of AD‾\overline{AD}. Given that line ACAC and line BEBE are perpendicular, find the greatest integer less than ADAD.

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Problem 4

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A group of children held a grape-eating contest. When the contest was over, the winner had eaten nn grapes, and the child in kk-th place had eaten n+2−2kn+2-2k grapes. The total number of grapes eaten in the contest was 20092009. Find the smallest possible value of nn.

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Problem 5

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Equilateral triangle TT is inscribed in circle AA, which has radius 1010. Circle BB with radius 33 is internally tangent to circle AA at one vertex of TT. Circles CC and DD, both with radius 22, are internally tangent to circle AA at the other two vertices of TT. Circles BB, CC, and DD are all externally tangent to circle EE, which has radius mn\dfrac mn, where mm and nn are relatively prime positive integers. Find m+nm+n. [asy] unitsize(3mm); defaultpen(linewidth(.8pt)); dotfactor=4; pair A=(0,0), D=8dir(330), C=8dir(210), B=7*dir(90); pair Ep=(0,4-27/5); pair[] dotted={A,B,C,D,Ep}; draw(Circle(A,10)); draw(Circle(B,3)); draw(Circle(C,2)); draw(Circle(D,2)); draw(Circle(Ep,27/5)); dot(dotted); label("EE",Ep,E); label("AA",A,W); label("BB",B,W); label("CC",C,W); label("DD",D,E); [/asy]

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Problem 6

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Let mm be the number of five-element subsets that can be chosen from the set of the first 1414 natural numbers so that at least two of the five numbers are consecutive. Find the remainder when mm is divided by 10001000.

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Problem 7

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Define n!!n!! to be n(n−2)(n−4)⋯3⋅1n(n-2)(n-4)\cdots 3\cdot 1 for nn odd and n(n−2)(n−4)⋯4⋅2n(n-2)(n-4)\cdots 4\cdot 2 for nn even. When ∑i=12009(2i−1)!!(2i)!!\sum_{i=1}^{2009} \frac{(2i-1)!!}{(2i)!!} is expressed as a fraction in lowest terms, its denominator is 2ab2^ab with bb odd. Find ab10\dfrac{ab}{10}.

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Problem 8

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Dave rolls a fair six-sided die until a six appears for the first time. Independently, Linda rolls a fair six-sided die until a six appears for the first time. Let mm and nn be relatively prime positive integers such that mn\dfrac mn is the probability that the number of times Dave rolls his die is equal to or within one of the number of times Linda rolls her die. Find m+nm+n.

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Problem 9

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Let mm be the number of solutions in positive integers to the equation 4x+3y+2z=20094x+3y+2z=2009, and let nn be the number of solutions in positive integers to the equation 4x+3y+2z=20004x+3y+2z=2000. Find the remainder when m−nm-n is divided by 10001000.

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Problem 10

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Four lighthouses are located at points AA, BB, CC, and DD. The lighthouse at AA is 55 kilometers from the lighthouse at BB, the lighthouse at BB is 1212 kilometers from the lighthouse at CC, and the lighthouse at AA is 1313 kilometers from the lighthouse at CC. To an observer at AA, the angle determined by the lights at BB and DD and the angle determined by the lights at CC and DD are equal. To an observer at CC, the angle determined by the lights at AA and BB and the angle determined by the lights at DD and BB are equal. The number of kilometers from AA to DD is given by pqr\frac {p\sqrt{q}}{r}, where pp, qq, and rr are relatively prime positive integers, and rr is not divisible by the square of any prime. Find pp + qq + rr.

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Problem 11

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For certain pairs (m,n)(m,n) of positive integers with m≥nm\geq n there are exactly 5050 distinct positive integers kk such that ∣log⁡m−log⁡k∣<log⁡n|\log m - \log k| < \log n. Find the sum of all possible values of the product mnmn.

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Problem 12

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From the set of integers {1,2,3,…,2009}\{1,2,3,\dots,2009\}, choose kk pairs {ai,bi}\{a_i,b_i\} with ai<bia_i<b_i so that no two pairs have a common element. Suppose that all the sums ai+bia_i+b_i are distinct and less than or equal to 20092009. Find the maximum possible value of kk.

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Problem 13

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Let AA and BB be the endpoints of a semicircular arc of radius 22. The arc is divided into seven congruent arcs by six equally spaced points C1C_1, C2C_2, …\dots, C6C_6. All chords of the form ACi‾\overline {AC_i} or BCi‾\overline {BC_i} are drawn. Let nn be the product of the lengths of these twelve chords. Find the remainder when nn is divided by 10001000.

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Problem 14

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The sequence (an)(a_n) satisfies a0=0a_0=0 and an+1=85an+654n−an2a_{n + 1} = \frac85a_n + \frac65\sqrt {4^n - a_n^2} for n≥0n\geq 0. Find the greatest integer less than or equal to a10a_{10}.

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Problem 15

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Let MN‾\overline{MN} be a diameter of a circle with diameter 1. Let AA and BB be points on one of the semicircular arcs determined by MN‾\overline{MN} such that AA is the midpoint of the semicircle and MB=35MB=\frac{3}5. Point CC lies on the other semicircular arc. Let dd be the length of the line segment whose endpoints are the intersections of diameter MN‾\overline{MN} with chords AC‾\overline{AC} and BC‾\overline{BC}. The largest possible value of dd can be written in the form r−str-s\sqrt{t}, where r,sr, s and tt are positive integers and tt is not divisible by the square of any prime. Find r+s+tr+s+t.

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