Subcontests
(40)Magnitudes of triangle ABC
The magnitudes of the sides of triangle ABC are a, b, and c, as shown, with c≤b≤a. Through interior point P and the vertices A, B, C, lines are drawn meeting the opposite sides in A′, B′, C′, respectively. Let s=AA′+BB′+CC′. Then, for all positions of point P, s is less than:<spanclass=′latex−bold′>(A)</span>2a+b<spanclass=′latex−bold′>(B)</span>2a+c<spanclass=′latex−bold′>(C)</span>2b+c<spanclass=′latex−bold′>(D)</span>a+2b<spanclass=′latex−bold′>(E)</span> a+b+c
[asy]
import math;
defaultpen(fontsize(11pt));
pair A = (0,0), B = (1,3), C = (5,0), P = (1.5,1);pair X = extension(B,C,A,P), Y = extension(A,C,B,P), Z = extension(A,B,C,P);draw(A--B--C--cycle);
draw(A--X);
draw(B--Y);
draw(C--Z);
dot(P);
dot(A);
dot(B);
dot(C);
label("A",A,dir(210));
label("B",B,dir(90));
label("C",C,dir(-30));
label("A′",X,dir(-100));
label("B′",Y,dir(65));
label("C′",Z,dir(20));
label("P",P,dir(70));
label("a",X,dir(80));
label("b",Y,dir(-90));
label("c",Z,dir(110));
//Credit to bobthesmartypants for the diagram
[/asy] Permissible positions of a circle
In this figure the radius of the circle is equal to the altitude of the equilateral triangle ABC. The circle is made to roll along the side AB, remaining tangent to it at a variable point T and intersecting lines AC and BC in variable points M and N, respectively. Let n be the number of degrees in arc MTN. Then n, for all permissible positions of the circle:<spanclass=′latex−bold′>(A)</span>varies from 30∘ to 90∘<spanclass=′latex−bold′>(B)</span>varies from 30∘ to 60∘<spanclass=′latex−bold′>(C)</span>varies from 60∘ to 90∘<spanclass=′latex−bold′>(D)</span>remains constant at 30∘<spanclass=′latex−bold′>(E)</span>remains constant at 60∘[asy]
pair A = (0,0), B = (1,0), C = dir(60), T = (2/3,0);
pair M = intersectionpoint(A--C,Circle((2/3,sqrt(3)/2),sqrt(3)/2)), N = intersectionpoint(B--C,Circle((2/3,sqrt(3)/2),sqrt(3)/2));draw((0,0)--(1,0)--dir(60)--cycle);
draw(Circle((2/3,sqrt(3)/2),sqrt(3)/2));
label("A",A,dir(210));
label("B",B,dir(-30));
label("C",C,dir(90));
label("M",M,dir(190));
label("N",N,dir(75));
label("T",T,dir(-90));
//Credit to bobthesmartypants for the diagram
[/asy] Find the missing length, PB
P is a point interior to rectangle ABCD and such that PA=3 inches, PD=4 inches, and PC=5 inches. Then PB, in inches, equals:<spanclass=′latex−bold′>(A)</span>23<spanclass=′latex−bold′>(B)</span>32<spanclass=′latex−bold′>(C)</span>33<spanclass=′latex−bold′>(D)</span>42<spanclass=′latex−bold′>(E)</span>2[asy]
draw((0,0)--(6.5,0)--(6.5,4.5)--(0,4.5)--cycle);
draw((2.5,1.5)--(0,0));
draw((2.5,1.5)--(0,4.5));
draw((2.5,1.5)--(6.5,4.5));
draw((2.5,1.5)--(6.5,0),linetype("8 8"));
label("A",(0,0),dir(-135));
label("B",(6.5,0),dir(-45));
label("C",(6.5,4.5),dir(45));
label("D",(0,4.5),dir(135));
label("P",(2.5,1.5),dir(-90));
label("3",(1.25,0.75),dir(120));
label("4",(1.25,3),dir(35));
label("5",(4.5,3),dir(120));
//Credit to bobthesmartypants for the diagram
[/asy] Application of SAS Similarity
In this figure ∠RFS=∠FDR, FD=4 inches, DR=6 inches, FR=5 inches, FS=721 inches. The length of RS, in inches, is:[asy]
import olympiad;
pair F,R,S,D;
F=origin;
R=5*dir(aCos(9/16));
S=(7.5,0);
D=4*dir(aCos(9/16)+aCos(1/8));
label("F",F,SW);label("R",R,N); label("S",S,SE); label("D",D,W);
label("721",(F+S)/2.5,SE);
label("4",midpoint(F--D),SW);
label("5",midpoint(F--R),W);
label("6",midpoint(D--R),N);
draw(F--D--R--F--S--R);
markscalefactor=0.1;
draw(anglemark(S,F,R)); draw(anglemark(F,D,R));
//Credit to throwaway1489 for the diagram[/asy]<spanclass=′latex−bold′>(A)</span> undetermined<spanclass=′latex−bold′>(B)</span> 4<spanclass=′latex−bold′>(C)</span> 521<spanclass=′latex−bold′>(D)</span> 6<spanclass=′latex−bold′>(E)</span> 641 Set values of m
The set of values of m for which x2+3xy+x+my−m has two factors, with integer coefficients, which are linear in x and y, is precisely:<spanclass=′latex−bold′>(A)</span> 0,12,−12<spanclass=′latex−bold′>(B)</span> 0,12<spanclass=′latex−bold′>(C)</span> 12,−12<spanclass=′latex−bold′>(D)</span> 12<spanclass=′latex−bold′>(E)</span> 0 Logs
If logb2x+logx2b=1,b>0,b=1,x=1, then x equals:<spanclass=′latex−bold′>(A)</span> 1/b2<spanclass=′latex−bold′>(B)</span> 1/b<spanclass=′latex−bold′>(C)</span> b2<spanclass=′latex−bold′>(D)</span> b<spanclass=′latex−bold′>(E)</span> b Points P, Q, R
Given the distinct points P(x1,y1), Q(x2,y2) and R(x1+x2,y1+y2). Line segments are drawn connecting these points to each other and to the origin 0. Of the three possibilities: (1) parallelogram (2) straight line (3) trapezoid, figure OPRQ, depending upon the location of the points P,Q, and R, can be:<spanclass=′latex−bold′>(A)</span> (1) only<spanclass=′latex−bold′>(B)</span> (2) only<spanclass=′latex−bold′>(C)</span> (3) only<spanclass=′latex−bold′>(D)</span> (1) or (2) only<spanclass=′latex−bold′>(E)</span> all three Set of Integers
Let f(x)=x2+3x+2 and let S be the set of integers {0,1,2,…,25}. The number of members s of S such that f(s) has remainder zero when divided by 6 is:<spanclass=′latex−bold′>(A)</span> 25<spanclass=′latex−bold′>(B)</span> 22<spanclass=′latex−bold′>(C)</span> 21<spanclass=′latex−bold′>(D)</span> 18<spanclass=′latex−bold′>(E)</span> 17 Negation of Statement
Which of the following is the negation of the statement: For all x of a certain set, x2>0?<spanclass=′latex−bold′>(A)</span> For all x,x2<0
<spanclass=′latex−bold′>(B)</span> For all x,x2≤0
<spanclass=′latex−bold′>(C)</span> For no x,x2>0
<spanclass=′latex−bold′>(D)</span> For some x,x2>0
<spanclass=′latex−bold′>(E)</span> For some x,x2≤0 Geometric Progression
If x,2x+2,3x+3,… are in geometric progression, the fourth term is:<spanclass=′latex−bold′>(A)</span> −27<spanclass=′latex−bold′>(B)</span> −1321<spanclass=′latex−bold′>(C)</span> 12<spanclass=′latex−bold′>(D)</span> 1321<spanclass=′latex−bold′>(E)</span> 27 Varies Directly...
If y varies directly as x, and if y=8 when x=4, the value of y when x=−8 is:<spanclass=′latex−bold′>(A)</span> −16<spanclass=′latex−bold′>(B)</span> −4<spanclass=′latex−bold′>(C)</span> −2<spanclass=′latex−bold′>(D)</span> 4k,k=±1,±2,…
<spanclass=′latex−bold′>(E)</span> 16k,k=±1,±2,…