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Probability of choosing integer coordinate points

Source: 2012 AMC 12A Problem #23

February 8, 2012
probabilityanalytic geometryAsymptotegeometryrectangletrigonometrygraphing lines

Problem Statement

Let SS be the square one of whose diagonals has endpoints (0.1,0.7)(0.1,0.7) and (0.1,0.7)(-0.1,-0.7). A point v=(x,y)v=(x,y) is chosen uniformly at random over all pairs of real numbers xx and yy such that 0x20120\le x \le 2012 and 0y20120 \le y \le 2012. Let T(v)T(v) be a translated copy of SS centered at vv. What is the probability that the square region determined by T(v)T(v) contains exactly two points with integer coordinates in its interior?
<spanclass=latexbold>(A)</span> 0.125<spanclass=latexbold>(B)</span> 0.14<spanclass=latexbold>(C)</span> 0.16<spanclass=latexbold>(D)</span> 0.25<spanclass=latexbold>(E)</span> 0.32 <span class='latex-bold'>(A)</span>\ 0.125\qquad<span class='latex-bold'>(B)</span>\ 0.14\qquad<span class='latex-bold'>(C)</span>\ 0.16\qquad<span class='latex-bold'>(D)</span>\ 0.25\qquad<span class='latex-bold'>(E)</span>\ 0.32