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 = <<80*5=400>>400 engines in total.
400/4 = <<400/4=100>>100 of the engines are defective.
400-100 = <<400-100=300>>300 of the engines are not defective.
#### 300