Question

The time t required to drive a certain distance varies inversely with the speed r. If it takes 2 hours to drive the distance at 40 miles per hour, how long will it take to drive the same distance at 45 miles per hour?

Answer 1

Answer: about 1.78 hours

Answer 2

1.78 hours

Explanation:

If t varies inversely with the speed, the formula for that is t= \frac{k}{r} . If t = 2 and r = 40, then we can solve for k, the constant of variation. Multiply both sides by 40 to get k = 80. Now we need to find the value for t when r = 45. Using the k value we just solved for, we will fill in the equation as t= \frac{80}{45} for a t value of about 1.78 hours