1988 AJHSME #5
Source:
June 21, 2011
Problem Statement
If is a right angle, then this protractor indicates that the measure of is approximately [asy]
unitsize(36);
pair A,B,C,D;
A=3*dir(160); B=origin; C=3*dir(110); D=3*dir(20);
draw((1.5,0)..(0,1.5)..(-1.5,0));
draw((2.5,0)..(0,2.5)..(-2.5,0)--cycle);
draw(A--B); draw(C--B); draw(D--B);
label("O",(-2.5,0),W);
label("A",A,W);
label("B",B,S);
label("C",C,W);
label("D",D,E);
label("0",(-1.8,0),W);
label("20",(-1.7,.5),NW);
label("160",(1.6,.5),NE);
label("180",(1.7,0),E);[/asy]