Tom needs to lower a rope down 6 stories.   One story is 10 feet.  The only rope being sold is 20 feet long but you lose 25% when lashing them together.  How many pieces of rope will he need to buy?
He needs 10*6=<T>multiply(10, 6)=60 feet
He loses 20*.25=<T>multiply(20, 0.25)=5.0 feet each time
So he gets 20-5=<T>subtract(20, 5)=15 feet from each piece
That means he needs 60/15=<T>divide(60, 15)=4.0 pieces of rope
