Practical Mathematics K8Doctors recommend scrubbing the hands with soap for at least 20 seconds, then rinsing them thoroughly. It usually takes 1 gallon (about 4 liters) of water to wash the hands according to the expert recommendation.

Gerry washes his hands ten times per day, each time taking about 10 seconds instead of 20 seconds.

How much water will have been spent washing his hands in a week?