Question

A water tank initially contained 62 liters of water. It is being drained at a constant rate of 2.5 liters per minute. How many liters of water are in the tank after 71 seconds? Round answers to the nearest whole liter.

Answer 1

We know that

• The initial condition is 62 liters of water.

,

• The constant rate is 2.5 liters per minute.

Remember that the initial condition represents the constant term of the equation, and the constant rate represents the coefficient of x. So, the equation that represents this problem is

`y=62-2.5x`

Notice that the rate is negative because the amount of water is decreasing.

Then, we evaluate this equation when for 71 seconds, which is equivalent to 1.18 minutes, so x = 1.18.

`y=62-2.5\cdot1.18=62-2.95=59.05`

Hence, there are 59.05 liters after 71 seconds.