Question

Before a rainstorm, there were already 15 centimeters of water in a reservoir.

After the rainstorm, there were 45 centimeters of water in the reservoir. The rain fell at a constant rate during the storm, and the storm lasted 5 hours.

If x represents the number of hours since the rainstorm started and y represents the number of centimeters of water in the reservoir, which function models this scenario?

A.

y = 6x + 5
B.

y = 6x + 15
C.

y = 5x + 6
D.

y = 15x + 6

Answer 1

Initial amount y(0) = 15 cm. After 5 hours y(5) = 45 cm, so the rate = (45−15)/5 = 6 cm/hour. Thus y = 6x + 15, choice B.