Multiply the fraction (35ft/sec) by the fractions:
(12inch / ft) · (2.54cm / inch) · (60sec / minute) · (60min / hr) .
Notice that each of these fractions has the same thing on the top and bottom. So each fraction is equal to " 1 ", and it doesn't change the value of your "35ft/sec" when you multiply them. It only converts the units.
As you muliply, keep all the units.
If you multiply everything correctly, you'll wind up with one big ugly fraction, with numbers and a bunch of units on top and bottom.
Cancel whatever you can from the numerator and denominator. If you do that correctly, you'll end up with units of " --- cm / --- hr " ... exactly what you want.
