21. The time, t, required to drive a certain distance varies inversely with the speed, r. If it takes 12 hours to drive the distance at 60 miles per hour, how long will it take to drive the same distance at 85 miles per hour?

Answer 1

We can start by using the inverse variation formula:

t = k/r

where k is the constant of variation. To find k, we can use the given information that it takes 12 hours to drive the distance at 60 miles per hour:

12 = k/60

Multiplying both sides by 60, we get:

k = 720

Now we can use this value of k to find the time required to drive the same distance at 85 miles per hour:

t = 720/85

t ≈ 8.47 hours

Therefore, it will take approximately 8.47 hours to drive the same distance at 85 miles per hour.