olymmath

AIME 2001b

American Invitational Mathematics Examination 2001.

Paper

Problem 1

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Let NN be the largest positive integer with the following property: reading from left to right, each pair of consecutive digits of NN forms a perfect square. What are the leftmost three digits of NN?

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Problem 2

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Each of the 20012001 students at a high school studies either Spanish or French, and some study both. The number who study Spanish is between 8080 percent and 8585 percent of the school population, and the number who study French is between 3030 percent and 4040 percent. Let mm be the smallest number of students who could study both languages, and let MM be the largest number of students who could study both languages. Find M−mM-m.

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Problem 3

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Given that \begin{align*}x_{1}&=211,\ x_{2}&=375,\ x_{3}&=420,\ x_{4}&=523,\ \text{and}\ x_{n}&=x_{n-1}-x_{n-2}+x_{n-3}-x_{n-4}\ \text{when}\ n\geq5, \end{align*} find the value of x531+x753+x975x_{531}+x_{753}+x_{975}.

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Problem 4

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Let R=(8,6)R = (8,6). The lines whose equations are 8y=15x8y = 15x and 10y=3x10y = 3x contain points PP and QQ, respectively, such that RR is the midpoint of PQ‾\overline{PQ}. The length of PQPQ equals mn\frac {m}{n}, where mm and nn are relatively prime positive integers. Find m+nm + n.

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Problem 5

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A set of positive numbers has the triangle property if it has three distinct elements that are the lengths of the sides of a triangle whose area is positive. Consider sets {4,5,6,…,n}\{4, 5, 6, \ldots, n\} of consecutive positive integers, all of whose ten-element subsets have the triangle property. What is the largest possible value of nn?

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Problem 6

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Square ABCDABCD is inscribed in a circle. Square EFGHEFGH has vertices EE and FF on CD‾\overline{CD} and vertices GG and HH on the circle. If the area of square ABCDABCD is 11, then the area of square EFGHEFGH can be expressed as mn\frac {m}{n} where mm and nn are relatively prime positive integers and m<nm < n. Find 10n+m10n + m.

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Problem 7

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Let △PQR\triangle{PQR} be a right triangle with PQ=90PQ = 90, PR=120PR = 120, and QR=150QR = 150. Let C1C_{1} be the inscribed circle. Construct ST‾\overline{ST} with SS on PR‾\overline{PR} and TT on QR‾\overline{QR}, such that ST‾\overline{ST} is perpendicular to PR‾\overline{PR} and tangent to C1C_{1}. Construct UV‾\overline{UV} with UU on PQ‾\overline{PQ} and VV on QR‾\overline{QR} such that UV‾\overline{UV} is perpendicular to PQ‾\overline{PQ} and tangent to C1C_{1}. Let C2C_{2} be the inscribed circle of △RST\triangle{RST} and C3C_{3} the inscribed circle of △QUV\triangle{QUV}. The distance between the centers of C2C_{2} and C3C_{3} can be written as 10n\sqrt {10n}. What is nn?

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Problem 8

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A certain function ff has the properties that f(3x)=3f(x)f(3x) = 3f(x) for all positive real values of xx, and that f(x)=1−∣x−2∣f(x) = 1-|x-2| for 1≤x≤31\le x \le 3. Find the smallest xx for which f(x)=f(2001)f(x) = f(2001).

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Problem 9

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Each unit square of a 3-by-3 unit-square grid is to be colored either blue or red. For each square, either color is equally likely to be used. The probability of obtaining a grid that does not have a 2-by-2 red square is mn\frac {m}{n}, where mm and nn are relatively prime positive integers. Find m+nm + n.

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Problem 10

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How many positive integer multiples of 10011001 can be expressed in the form 10j−10i10^{j} - 10^{i}, where ii and jj are integers and 0≤i<j≤990\leq i < j \leq 99?

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Problem 11

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Club Truncator is in a soccer league with six other teams, each of which it plays once. In any of its 6 matches, the probabilities that Club Truncator will win, lose, or tie are each 13\frac {1}{3}. The probability that Club Truncator will finish the season with more wins than losses is mn\frac {m}{n}, where mm and nn are relatively prime positive integers. Find m+nm + n.

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Problem 12

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Given a triangle, its midpoint triangle is obtained by joining the midpoints of its sides. A sequence of polyhedra PiP_{i} is defined recursively as follows: P0P_{0} is a regular tetrahedron whose volume is 1. To obtain Pi+1P_{i + 1}, replace the midpoint triangle of every face of PiP_{i} by an outward-pointing regular tetrahedron that has the midpoint triangle as a face. The volume of P3P_{3} is mn\frac {m}{n}, where mm and nn are relatively prime positive integers. Find m+nm + n.

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Problem 13

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In quadrilateral ABCDABCD, ∠BAD≅∠ADC\angle{BAD}\cong\angle{ADC} and ∠ABD≅∠BCD\angle{ABD}\cong\angle{BCD}, AB=8AB = 8, BD=10BD = 10, and BC=6BC = 6. The length CDCD may be written in the form mn\frac {m}{n}, where mm and nn are relatively prime positive integers. Find m+nm + n.

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Problem 14

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There are 2n2n complex numbers that satisfy both z28−z8−1=0z^{28} - z^{8} - 1 = 0 and ∣z∣=1\mid z \mid = 1. These numbers have the form zm=cos⁡θm+isin⁡θmz_{m} = \cos\theta_{m} + i\sin\theta_{m}, where 0≤θ1<θ2<…<θ2n<3600\leq\theta_{1} < \theta_{2} < \ldots < \theta_{2n} < 360 and angles are measured in degrees. Find the value of θ2+θ4+…+θ2n\theta_{2} + \theta_{4} + \ldots + \theta_{2n}.

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Problem 15

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Let EFGHEFGH, EFDCEFDC, and EHBCEHBC be three adjacent square faces of a cube, for which EC=8EC = 8, and let AA be the eighth vertex of the cube. Let II, JJ, and KK be the points on EF‾\overline{EF}, EH‾\overline{EH}, and EC‾\overline{EC}, respectively, so that EI=EJ=EK=2EI = EJ = EK = 2. A solid SS is obtained by drilling a tunnel through the cube. The sides of the tunnel are planes parallel to AE‾\overline{AE}, and containing the edges, IJ‾\overline{IJ}, JK‾\overline{JK}, and KI‾\overline{KI}. The surface area of SS, including the walls of the tunnel, is m+npm + n\sqrt {p}, where mm, nn, and pp are positive integers and pp is not divisible by the square of any prime. Find m+n+pm + n + p.

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