Bill drives his car 10 mph faster on the way home from work than he does going to work in rush hour. If it takes him 1 hrs. going and half an hour returning, how far away is his work?

Answer 1

Speed = r mi/h going to work.
Speed = (r+10)m/h returning.

d = r mi/h * 1 h = (r+10)mi/h * 0.5h
r * 1 = (r+10) * 0.5
r = 0.5r + 5
0.5r = 5
r = 10 mi/h
r+10 = 10+10 = 20 mi/h

d = 10 * 1 = (10+10) * 0.5 = 10 mi.