how far from the base of a 10ft ladder be placed so that it reaches 8ft up the wall

Answer 1

You probably meant to ask:
"How far from the base should a 10ft ladder be placed so that it reaches 8ft up the wall ?"

solve for b
b^2 + 8^2 = 10^2

Answer 2

Since we know that the ladder is like the hypotenuse of a right triangle, we use the Pythagorous theorem. Which is what the person above used.

any Right (90 degree) triangle with height (a) and base (b) has a hypotenuse (c) where

a^2 + b^2 = c^2