# Thread: another trigonometry word problem

1. ## another trigonometry word problem

Electric Motor. if a 2 inch diameter pulley that's being driven by an electric motor and running at 1600 revolutions per minute is connected by a belt to a 5 inch diameter pulley to drive a saw, what is the speed of the saw in revolutions per minute?

2. Originally Posted by 08gakawa
Electric Motor. if a 2 inch diameter pulley that's being driven by an electric motor and running at 1600 revolutions per minute is connected by a belt to a 5 inch diameter pulley to drive a saw, what is the speed of the saw in revolutions per minute?
Use the same method as angel.white has described here http://www.mathhelpforum.com/math-he...306-post2.html

The product of revolutions times circumferences must be constant:

$r_1 \cdot c_1 = r_2 \cdot c_2$ . Plug in the values you know:

$1600 \cdot 2\pi = r_2 \cdot 5\pi$ . Solve for $r_2$.

(For confirmation only: $r_2 = 640$ )