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The top of a ladder slides down a vertical wall at a rate of 0.675 m/s. At the moment when the bottom of the ladder is 3 m from the wall, it slides away from the wall at a rate of 0.9 m/s. How long is the ladder?

Verified Answer :

Let the length of the ladder be L we have comparing lengths after 1s and applying Pythagoras theorem. 
(3 + 0.9)^2 + {√(L^2-9) - 0.675} ^2 = L^2 or 
9 + 1.8 + 0.81 + (L^2-9) + 0.455625 - 1.35*√(L^2-9) = L^2 or 
√(L^2-9) = 8.9375 or (L^2-9) = 79.87890625 
or L = 9.43 m

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