Padding 7 miles upstream, Steven and his brother averaged 2 miles per hour. On the way back, their rate of speed was 3 1/2 miles per hour. How long did it take them to make the round trip?
Time for going upwqards=7/2=3.5 hrs
Time for coming back=7/3.5=2 hrs
Total 3.5+2=5.5 i.e. 5 1/2 hrs