olymmath

AIME 2000b

American Invitational Mathematics Examination 2000.

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Problem 2

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A point whose coordinates are both integers is called a lattice point. How many lattice points lie on the hyperbola x2−y2=20002x^2 - y^2 = 2000^2?

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Problem 3

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A deck of forty cards consists of four 11's, four 22's,..., and four 1010's. A matching pair (two cards with the same number) is removed from the deck. Given that these cards are not returned to the deck, let mn\frac{m}{n} be the probability that two randomly selected cards also form a pair, where mm and nn are relatively prime positive integers. Find m+n.m + n.

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Problem 5

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Given eight distinguishable rings, let nn be the number of possible five-ring arrangements on the four fingers (not the thumb) of one hand. The order of rings on each finger is significant, but it is not required that each finger have a ring. Find the leftmost three nonzero digits of nn.

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Problem 6

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One base of a trapezoid is 100100 units longer than the other base. The segment that joins the midpoints of the legs divides the trapezoid into two regions whose areas are in the ratio 2:32: 3. Let xx be the length of the segment joining the legs of the trapezoid that is parallel to the bases and that divides the trapezoid into two regions of equal area. Find the greatest integer that does not exceed x2/100x^2/100.

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Problem 8

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In trapezoid ABCDABCD, leg BC‾\overline{BC} is perpendicular to bases AB‾\overline{AB} and CD‾\overline{CD}, and diagonals AC‾\overline{AC} and BD‾\overline{BD} are perpendicular. Given that AB=11AB=\sqrt{11} and AD=1001AD=\sqrt{1001}, find BC2BC^2.

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Problem 9

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Given that zz is a complex number such that z+1z=2cos⁡3∘z+\frac 1z=2\cos 3^\circ, find the least integer that is greater than z2000+1z2000z^{2000}+\frac 1{z^{2000}}.

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Problem 10

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A circle is inscribed in quadrilateral ABCDABCD, tangent to AB‾\overline{AB} at PP and to CD‾\overline{CD} at QQ. Given that AP=19AP=19, PB=26PB=26, CQ=37CQ=37, and QD=23QD=23, find the square of the radius of the circle.

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Problem 11

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The coordinates of the vertices of isosceles trapezoid ABCDABCD are all integers, with A=(20,100)A=(20,100) and D=(21,107)D=(21,107). The trapezoid has no horizontal or vertical sides, and AB‾\overline{AB} and CD‾\overline{CD} are the only parallel sides. The sum of the absolute values of all possible slopes for AB‾\overline{AB} is m/nm/n, where mm and nn are relatively prime positive integers. Find m+nm+n.

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Problem 12

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The points AA, BB and CC lie on the surface of a sphere with center OO and radius 2020. It is given that AB=13AB=13, BC=14BC=14, CA=15CA=15, and that the distance from OO to △ABC\triangle ABC is mnk\frac{m\sqrt{n}}k, where mm, nn, and kk are positive integers, mm and kk are relatively prime, and nn is not divisible by the square of any prime. Find m+n+km+n+k.

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Problem 13

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The equation 2000x6+100x5+10x3+x−2=02000x^6+100x^5+10x^3+x-2=0 has exactly two real roots, one of which is m+nr\frac{m+\sqrt{n}}r, where mm, nn and rr are integers, mm and rr are relatively prime, and r>0r>0. Find m+n+rm+n+r.

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Problem 14

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Every positive integer kk has a unique factorial base expansion (f1,f2,f3,…,fm)(f_1,f_2,f_3,\ldots,f_m), meaning that k=1!⋅f1+2!⋅f2+3!⋅f3+⋯+m!⋅fmk=1!\cdot f_1+2!\cdot f_2+3!\cdot f_3+\cdots+m!\cdot f_m, where each fif_i is an integer, 0≤fi≤i0\le f_i\le i, and 0<fm0<f_m. Given that (f1,f2,f3,…,fj)(f_1,f_2,f_3,\ldots,f_j) is the factorial base expansion of 16!−32!+48!−64!+⋯+1968!−1984!+2000!16!-32!+48!-64!+\cdots+1968!-1984!+2000!, find the value of f1−f2+f3−f4+⋯+(−1)j+1fjf_1-f_2+f_3-f_4+\cdots+(-1)^{j+1}f_j.

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