A salesman keeps 20% of his sales as a commission. How much does he have to sell to earn $1000?

We could do some fancy math here....but......since he gets only 1/5 of what he sells, then he has to sell 5 times as much $1000 = $5000 in order to make $1000

...Does that make sense ???

5000 * 0.20 = 1000