Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 6 hours and Jill can run a marathon in 4.2 hours.What is the ratio of their average running speed? (Jack: Jill)  Choose the most appropriate option.
A) 7/10	B) 15/14	C) 4/5	D) 5/4	E) Cannot be determined
7/10verage Speed of Jack =Distance/ Time   = 42 /6= 
<gadget id="calculator">42 /6</gadget>
<output>7</output>
7   7/10verage Speed of Jill= 42/(4.2)= 
<gadget id="calculator">42/(4.2)</gadget>
<output>10</output>
10   Ratio of 7/10verage speed of Jack to Jill= 7/10   7/10nswer 7/10
<result>A</result>
Jack and Jill are marathon runners. Jack can finish a marathon (42 km) in 6 hours and Jill can run a marathon in 4.2 hours.What is the ratio of their average running speed? (Jack: Jill)