Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 7 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) 5/5
D) 5/4
E) Cannot be determined
Average Speed of Jack =Distance/ Time   = 42 /7= 
<gadget id="calculator">42 /7</gadget>
<output>6</output>
6   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=6/10 = 3/5   Answer 5/5
<result>C</result>
Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 7 hours and Jill can run a marathon in 4.2 hours.What is the ratio of their average running speed? (Jack: Jill)