Sam left his school at 3:05. He walked at a speed of 3.5 mph. 15 minutes later, Al started running after him, and he caught up with Sam 20 minutes later. What was Al’s speed?
+37146 Sam has a 1/4 hr head start at 3.5 m/hr
3.5 m/h x 1/4 hr = .875 miles
Al closes this distance in 20 minutes = 1/3 hr
he is thus moving .875 m/1/3 hr FASTER than Sam = 2.625 m/hr faster
3.5 + 2.625 = 6.125 m/hr
