2015 AMC 8 #19
Source:
November 25, 2015
AMC 8coordinatePick's theorembarycentric coordinates
Problem Statement
A triangle with vertices as , , and is plotted on a grid. What fraction of the grid is covered by the triangle?[asy]draw((1,0)--(1,5),linewidth(.5));
draw((2,0)--(2,5),linewidth(.5));
draw((3,0)--(3,5),linewidth(.5));
draw((4,0)--(4,5),linewidth(.5));
draw((5,0)--(5,5),linewidth(.5));
draw((6,0)--(6,5),linewidth(.5));
draw((0,1)--(6,1),linewidth(.5));
draw((0,2)--(6,2),linewidth(.5));
draw((0,3)--(6,3),linewidth(.5));
draw((0,4)--(6,4),linewidth(.5));
draw((0,5)--(6,5),linewidth(.5));
draw((0,0)--(0,6),EndArrow);
draw((0,0)--(7,0),EndArrow);
draw((1,3)--(4,4)--(5,1)--cycle);
label("",(0,6),W); label("",(7,0),S);
label("",(1,3),dir(230)); label("",(5,1),SE); label("",(4,4),dir(50));
[/asy]