# Net change (graphical)

Practice associating the area under rate-of-change curves with net change.

### Problem

Firemen use one hose to spray water on a house fire at a rate of 12 gallons per minute. After 20 minutes, the firemen connect a second hose to a hydrant to double the total spray rate. It takes 100 minutes to put out the fire. The graph below shows the spray rate as a function of time.
How much water do the firemen use to put out the fire?
gallons