Every evening, Mr. Fat walks around a square city block once. Beginning at a corner, he would walk the first three sides at 6 feet per second and the final side at 5 feet per second. What is his average speed in feet per second? Express your answer as an improper fraction.
x= side length.
X/6 time for one side at 6 f/s
x/5 time for one side at 5f/s
4x / (x/6. + x/6. +x/6. + x /5)
40/7=40/7 = 5.7142857142857143 f/sec avg