Question

Mary ran the 5 kilometre race in 45 minutes. Melanie ran the 2 kilometre race in 17 minutes. Which runner ran the faster race? What was that rate per hour

Answer 1

Mary ran the 5 kilometre race in 45 minutes.
45 minutes = 3/4 of an hour
This means that her speed is 
S/t=5/(3/4)=20/3 = 6+2/3  (km / hour)
Melanie ran the 2 kilometre race in 17 minutes. 
17 minutes = 17/60 of an hour
This means that her speed is 
S/t=2/(17/60)=120/17= 7+1/17 (km / hour)
So, Melanie is faster than Mary.