<human>:  If one fourth of the engines are defective, and there are 5 batches of 80 engines each. How many engines are not defective?
<bot>: How many engines total are there? ** There are 80*5 = <<80*5=400>>400 engines in total.
How many engines are defective? ** 400/4 = <<400/4=100>>100 of the engines are defective.
How many engines are not defective? ** 400-100 = <<400-100=300>>300 of the engines are not defective.
#### 300