# Math Help - Rate of Change Word Problem

1. ## Rate of Change Word Problem

A construction worker at the top of a building is pulling, with a rope, one end of a five-meter plank up a buildings vertical side. The non-rope end of the plank rests on the ground. Therefore the buildings side, plank, and ground form a right triangle. If the rope end of the plank is being pulled up at a rate of 0.15 m/sec. How fast (rate of change) is the other end of the plank moving toward the base of the building when the end of the non-rope end is 2.5 meters from the building?

Last problem on my HW sheet and it's really giving me trouble

Any help would be really great

Thanks!

2. This is like the related rates ladder problems.

$x^{2}+y^{2}=25$

$\frac{dx}{dt}=\frac{-y}{x}\cdot\frac{dy}{dt}$

Use Pythagoras to find y given x=5/2 and the hypoteneuse of the triangle is 5, then you have all the info to find dx/dt