James wants to build a ladder to climb a very tall tree.  Each rung of the ladder is 18 inches long and they are 6 inches apart.  If he needs to climb 50 feet how many feet of wood will he need for the rungs?
He needs 12/6=2 rungs per foot
So he needs 50*2=100 rungs
Each rung is 18/12=1.5 feet
So he needs 1.5*100=150 feet