DAY 332

You have to drive 40 miles round trip. You drove the first half at 15 mph. How fast do you have to drive the second half to average 20 mph?

Answer:

30 mph........ To drive 40 miles at an average speed of 20 mph would take 2 hours:

(D = RT ------ 40 = 20 T). The first 1/2 (20 miles) has taken you 1 hour 20 minutes

(20 = 15 T) ------ T = 1 1/3 hours). So you must drive the second 20 miles in 40 minutes or 2/3 of an hour.

20 = R 2/3

R = 30.