Adam drove the 10 miles to school at a speed of 60 mph. On his way home, due to traffic, his speed w

Adam drove the 10 miles to school at a speed of 60 mph. On his way home, due to traffic, his speed was 30 mph. What was his average speed for the round trip to school and back?

D = rt

To school:
60 miles in 60 minutes = 10 miles in 10 minutes

To home:
30 miles in 60 minutes = 10 miles in 20 minutes

Total time:
10 + 20 = 30 minutes or 0.5 hours

With a speed of s, we have:
d = st
20 = 0.5s

Divide each side by 2:
s = 40 mph