Question

Javier walks up to a tank of water that can hold up to 10 gallons. When it is active, a drain empties water from the tank at a constant rate. When Javier first sees the tank, it contains 7 gallons of water. Three minutes later, the tank contains 5 gallons of water.

At what rate is the amount of water in the tank changing? Use a signed number, and include the unit of measurement in your answer.

How many more minutes will it take for the tank to drain completely? Explain or show your reasoning.

How many minutes before Javier arrived was the water tank completely full? Explain or show your reasoning.

Answer 1

Answer:1) Gallons per minute change is -2/3 gallons per minute since it decreases by 2 gallons in 3 minutes

2) we have 5 gallons and lose 2/3 gallons per minute

(2/3 gal/minute)(x minutes) = 5 gallons

x = 5(3/2) = 15/2 = 7.5 minutes to drain the other 5 gallons

3) There were 10 gallons when the tank is full

That is 3 gallons more than the 7 gals there when Jada arrived.

(2/3)(x) = 3

x = 3(3/2) = 9/2 = 4 1/2 minutes

The tank was full 4 1/2 minutes before Jada arrived.