Math Help, Practicing for SAT

Chester the dog has a chain that has a range of 100 feeth from his doghouse. Chester pulls on the chain and walks 80 feet due south. From that point he walks due west and stops at the maximum range of the chain. In which of the following directions can Chester walk and still be within the range of the chain?

I. North
II. South
III. East

a) II only
b) III only
c)I and II
d) I and III
e) II and III

d) I and III
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Ideas: Use 6-8-10 Pythagorean triple.

Draw yourself a diagram...

There's only two of the four directions that stay within 100 feet of where chester is now: the opposites of the directions already taken - north and east.