olymmath

AIME 2014a

American Invitational Mathematics Examination 2014.

Paper

Problem 1

  • Paper
  • Answer

The 8 eyelets for the lace of a sneaker all lie on a rectangle, four equally spaced on each of the longer sides. The rectangle has a width of 50 mm and a length of 80 mm. There is one eyelet at each vertex of the rectangle. The lace itself must pass between the vertex eyelets along a width side of the rectangle and then crisscross between successive eyelets until it reaches the two eyelets at the other width side of the rectangle as shown. After passing through these final eyelets, each of the ends of the lace must extend at least 200 mm farther to allow a knot to be tied. Find the minimum length of the lace in millimeters. [asy] size(200); defaultpen(linewidth(0.7)); path laceL=(-20,-30)..tension 0.75 ..(-90,-135)..(-102,-147)..(-152,-150)..tension 2 ..(-155,-140)..(-135,-40)..(-50,-4)..tension 0.8 ..origin; path laceR=reflect((75,0),(75,-240))laceL; draw(origin--(0,-240)--(150,-240)--(150,0)--cycle,gray); for(int i=0;i<=3;i=i+1) { path circ1=circle((0,-80i),5),circ2=circle((150,-80*i),5); unfill(circ1); draw(circ1); unfill(circ2); draw(circ2); } draw(laceL--(150,-80)--(0,-160)--(150,-240)--(0,-240)--(150,-160)--(0,-80)--(150,0)^^laceR,linewidth(1));[/asy]

Answer, solutions and source

Problem 2

  • Paper
  • Answer

An urn contains 44 green balls and 66 blue balls. A second urn contains 1616 green balls and NN blue balls. A single ball is drawn at random from each urn. The probability that both balls are of the same color is 0.580.58. Find NN.

Answer, solutions and source

Problem 3

  • Paper
  • Answer

Find the number of rational numbers rr, 0<r<10<r<1, such that when rr is written as a fraction in lowest terms, the numerator and the denominator have a sum of 1000.

Answer, solutions and source

Problem 4

  • Paper
  • Answer

Jon and Steve ride their bicycles along a path that parallels two side-by-side train tracks running the east/west direction. Jon rides east at 2020 miles per hour, and Steve rides west at 2020 miles per hour. Two trains of equal length, traveling in opposite directions at constant but different speeds each pass the two riders. Each train takes exactly 11 minute to go past Jon. The westbound train takes 1010 times as long as the eastbound train to go past Steve. The length of each train is mn\tfrac{m}{n} miles, where mm and nn are relatively prime positive integers. Find m+nm+n.

Answer, solutions and source

Problem 5

  • Paper
  • Answer

Let the set S={P1,P2,…,P12}S = \{P_1, P_2, \dots, P_{12}\} consist of the twelve vertices of a regular 1212-gon. A subset QQ of SS is called "communal" if there is a circle such that all points of QQ are inside the circle, and all points of SS not in QQ are outside of the circle. How many communal subsets are there? (Note that the empty set is a communal subset.)

Answer, solutions and source

Problem 6

  • Paper
  • Answer

The graphs y=3(x−h)2+jy=3(x-h)^2+j and y=2(x−h)2+ky=2(x-h)^2+k have y-intercepts of 20132013 and 20142014, respectively, and each graph has two positive integer x-intercepts. Find hh.

Answer, solutions and source

Problem 7

  • Paper
  • Answer

Let ww and zz be complex numbers such that ∣w∣=1|w| = 1 and ∣z∣=10|z| = 10. Let θ=arg⁡(w−zz)\theta = \arg \left(\tfrac{w-z}{z}\right). The maximum possible value of tan⁡2θ\tan^2 \theta can be written as pq\tfrac{p}{q}, where pp and qq are relatively prime positive integers. Find p+qp+q. (Note that arg⁡(w)\arg(w), for w≠0w \neq 0, denotes the measure of the angle that the ray from 00 to ww makes with the positive real axis in the complex plane)

Answer, solutions and source

Problem 8

  • Paper
  • Answer

The positive integers NN and N2N^2 both end in the same sequence of four digits abcdabcd when written in base 1010, where digit aa is not zero. Find the three-digit number abcabc.

Answer, solutions and source

Problem 9

  • Paper
  • Answer

Let x1<x2<x3x_1<x_2<x_3 be the three real roots of the equation 2014x3−4029x2+2=0\sqrt{2014}x^3-4029x^2+2=0. Find x2(x1+x3)x_2(x_1+x_3).

Answer, solutions and source

Problem 10

  • Paper
  • Answer

A disk with radius 11 is externally tangent to a disk with radius 55. Let AA be the point where the disks are tangent, CC be the center of the smaller disk, and EE be the center of the larger disk. While the larger disk remains fixed, the smaller disk is allowed to roll along the outside of the larger disk until the smaller disk has turned through an angle of 360∘360^\circ. That is, if the center of the smaller disk has moved to the point DD, and the point on the smaller disk that began at AA has now moved to point BB, then AC‾\overline{AC} is parallel to BD‾\overline{BD}. Then sin⁡2(∠BEA)=mn\sin^2(\angle BEA)=\tfrac{m}{n}, where mm and nn are relatively prime positive integers. Find m+nm+n.

Answer, solutions and source

Problem 11

  • Paper
  • Answer

A token starts at the point (0,0)(0,0) of an xyxy-coordinate grid and then makes a sequence of six moves. Each move is 1 unit in a direction parallel to one of the coordinate axes. Each move is selected randomly from the four possible directions and independently of the other moves. The probability the token ends at a point on the graph of ∣y∣=∣x∣|y|=|x| is mn\frac{m}{n}, where mm and nn are relatively prime positive integers. Find m+nm+n.

Answer, solutions and source

Problem 12

  • Paper
  • Answer

Let A={1,2,3,4}A=\{1,2,3,4\}, and ff and gg be randomly chosen (not necessarily distinct) functions from AA to AA. The probability that the range of ff and the range of gg are disjoint is mn\tfrac{m}{n}, where mm and nn are relatively prime positive integers. Find mm.

Answer, solutions and source

Problem 13

  • Paper
  • Answer

On square ABCDABCD, points E,F,GE,F,G, and HH lie on sides AB‾,BC‾,CD‾,\overline{AB},\overline{BC},\overline{CD}, and DA‾,\overline{DA}, respectively, so that EG‾⊥FH‾\overline{EG} \perp \overline{FH} and EG=FH=34EG=FH = 34. Segments EG‾\overline{EG} and FH‾\overline{FH} intersect at a point PP, and the areas of the quadrilaterals AEPH,BFPE,CGPF,AEPH, BFPE, CGPF, and DHPGDHPG are in the ratio 269:275:405:411.269:275:405:411. Find the area of square ABCDABCD. [asy] pair A = (0,sqrt(850)); pair B = (0,0); pair C = (sqrt(850),0); pair D = (sqrt(850),sqrt(850)); draw(A--B--C--D--cycle); dotfactor = 3; dot("AA",A,dir(135)); dot("BB",B,dir(215)); dot("CC",C,dir(305)); dot("DD",D,dir(45)); pair H = ((2sqrt(850)-sqrt(306))/6,sqrt(850)); pair F = ((2sqrt(850)+sqrt(306)+7)/6,0); dot("HH",H,dir(90)); dot("FF",F,dir(270)); draw(H--F); pair E = (0,(sqrt(850)-6)/2); pair G = (sqrt(850),(sqrt(850)+sqrt(100))/2); dot("EE",E,dir(180)); dot("GG",G,dir(0)); draw(E--G); pair P = extension(H,F,E,G); dot("PP",P,dir(60)); label("ww", intersectionpoint( A--P, E--H )); label("xx", intersectionpoint( B--P, E--F )); label("yy", intersectionpoint( C--P, G--F )); label("zz", intersectionpoint( D--P, G--H ));[/asy]

Answer, solutions and source

Problem 14

  • Paper
  • Answer

Let mm be the largest real solution to the equation 3x−3+5x−5+17x−17+19x−19=x2−11x−4\frac{3}{x-3}+\frac{5}{x-5}+\frac{17}{x-17}+\frac{19}{x-19}=x^2-11x-4 There are positive integers aa, bb, and cc such that m=a+b+cm=a+\sqrt{b+\sqrt{c}}. Find a+b+ca+b+c.

Answer, solutions and source

Problem 15

  • Paper
  • Answer

In △ABC\triangle ABC, AB=3AB = 3, BC=4BC = 4, and CA=5CA = 5. Circle ω\omega intersects AB‾\overline{AB} at EE and BB, BC‾\overline{BC} at BB and DD, and AC‾\overline{AC} at FF and GG. Given that EF=DFEF=DF and DGEG=34\frac{DG}{EG} = \frac{3}{4}, length DE=abcDE=\frac{a\sqrt{b}}{c}, where aa and cc are relatively prime positive integers, and bb is a positive integer not divisible by the square of any prime. Find a+b+ca+b+c.

Answer, solutions and source