A washing machine is filling up with water at a constant rate. The rate is 3/4 of a gallon in 1/5 of a minute. Don Calculated the unit rate to be 3/20 of a gallon per minute. What did he do wrong?

First, you have to see how many gallons fill in a minute, obviously, so take 3/4 and divide it by 1/5, which gives 15/4. so you can see, don multiplied the two numbers instead of dividing, which is what he did wrong.