peter walked from p --> q and back a total of 2 miles. He walked 4 mph on the trip from p to q and 5 mph on the return trip. What is his average speed?

Answer 1

Don't be tempted to average his speed.

Distance = velocity times time (D = VT) so T = D/V. On the first leg of his journey, Peter took 2/4 = 0.5 hours.

On his return trip he took 2/5 = 0.4 hours. His total time was 0.5 + 0.4 = 0.9 hours. His total distance was 4 miles. So his average speed was (4 miles)/(0.9 hours) = 4.44 mph

Answer 2

Don't be tempted to average his speed.

Distance = velocity times time (D = VT) so T = D/V. On the first leg of his journey, Peter took 2/4 = 0.5 hours.

On his return trip he took 2/5 = 0.4 hours. His total time was 0.5 + 0.4 = 0.9 hours. His total distance was 4 miles. So his average speed was (4 miles)/(0.9 hours) = 4.44 mph