Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 5.5 hours and Jill can run a marathon in 4.2 hours.What is the ratio of their average running speed? (Jack: Jill) Pick one:
A) 14/15  B) 15/14  C) 4/5  D) 42/55  E) Cannot be determined
Average Speed of Jack =42/55istance/ Time   = 42 /(11/2) = 84/11   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= (84/11)/10 = 84/110 = 42/55   Answer 42/55
<result>D</result>
Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 5.5 hours and Jill can run a marathon in 4.2 hours.What is the ratio of their average running speed? (Jack: Jill)