1. Sully drove from Atlanta, Georgia, to Birmingham, Alabama, a distance of 150 miles, at a mean speed of 50 miles per hour. On his return trip, the traffic was much lighter, and his mean speed was 60...

1. Sully drove from Atlanta, Georgia, to Birmingham, Alabama, a distance of 150 miles, at a mean speed of 50 miles per hour. On his return trip, the traffic was much lighter, and his mean speed was 60 miles per hour. Find Sully’s mean speed for the round trip.

HINT: Divide the total distance by the total time.

2. The mean age of a class of twenty ­five students is 23.4 years. How old would a twenty­ sixth student have to be for the mean age of the class to be 24.0 years?

3. The mean age of a class of fifteen students is 18.2 years. How old would a sixteenth student have to be for the mean age of the class to be 21.0 years?