If one fourth of the engines are defective, and there are 5 batches of 80 engines each. How many engines are not defective?
There are 80*5 = <T>multiply(80, 5)=400 engines in total.
400/4 = <T>divide(400, 4)=100.0 of the engines are defective.
400-100 = <T>subtract(400, 100)=300 of the engines are not defective.
