Question

Bill and Amy want to ride their bikes from their neighborhood to school which is 14.4 km away. It takes Amy 40 minutes to arrive at school. Bill arrives 20 minutes after Amy. How much faster (in km/h) is Amy than Bill for the entire trip?

Answer 1

Amy is (21.6 - 14.4) 7.2 km/hr faster than Bill.

Distance = speed / time

Amy's speed

40 minutes = 40/60 = 2/3 hours

14.4 = speed / 2/3

Speed = 14.4 * 3/2 = 21.6 km/ hr

Bill speed

60 minutes = 1 hour

Speed = 14.4 km / hr.