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Right triangle PQR is to be constructed in the xy-plane so [#permalink]
26 Feb 2008, 18:51
248. Right triangle PQR is to be constructed in the xy-plane so that the right angle is at P and PR is parallel to the x-axis. The x- and y- coordinates of P, Q and R are to be integers that satisfy the inequalities -4≤x≤5 and 6≤y≤16. how many different triangles with these properties could be contructed?
A. 110 B. 1100 C. 9900 D. 10000 E. 12100 _________________
10 ways to choose first x coordinate 9 ways to choose second x coordinate along same parallel line 11 ways to choose which level of y this is occuring at
# of ways to have 3rd vertex:
because we already have a base parallel to the x-axis, now we need one more line for the vertex. It has to have the same x coordinate (since it's a right angle) so there are 10 other y values it could have