A boy walks 800m in 20 minutes. Calculate his average speed in km per hour

A.
2.4 
B.
4 
C.
16 
D.
24
Correct Answer: Option A
Explanation
(Average hspace{1mm}speed = frac{Distance}{Timehspace{1mm} taken}\
Distance = 800m = frac{800}{1000}km = 0.8km\
Timehspace{1mm}taken = 20hspace{1mm}minutes = frac{20}{60}hr=frac{1}{3}hr\Average hspace{1mm} speed = left(0.8div frac{1}{3}right)km/hr = (0.8times3)km/hr\=2.4km/hr)