Question

Solve the problem.

The temperature of water in a certain lake on a day in October can be determined by using the model = 15.2-0.537x
where x is the number of feet down from the surface of the lake and y is the Celsius temperature of the water at that
depth. Based on this model, how deep in the lake is the water 9 degrees? (Round to the nearest foot.)
a. 12
b. 45
c.
67
d. 30

Answer 1

Answer: 12 ft

Explanation:

Our equation is y = 15.2 - .537x where "y" is the temperature and "x" is the depth. We want to find the depth when the temperature is 9 degrees. Therefore, we need to plug in y = 9 and find x:

9 = 15.2 - .537x

We subtract 15.2 from both sides and divide by -1 on both sides so that we are working with positive numbers only:

6.2 = .537x

We then divide both sides by .537 to isolate x:

11.55 = x

This rounds to 12, meaning that at 9 degrees, the depth is 12ft.