Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 5 hours and Jill can run a marathon in 4.2 hours.What is the ratio of their average running speed? (Jack: Jill)	Choose one:
A) 14/15  B) 15/14  C) 4/5  D) 21/25  E) Cannot be determined
Average Speed of Jack =21/25istance/ Time   = 42 /5   Average Speed of Jill = 42/(4.2)= 
<gadget id="calculator">42/(4.2)</gadget>
<output>10</output>
10   Ratio of Average speed of Jack to Jill= (42/5)/10 =42/50 =21/25   Answer 21/25
<result>D</result>
Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 5 hours and Jill can run a marathon in 4.2 hours.What is the ratio of their average running speed? (Jack: Jill)