A car covers `(1)/(3)`part of total distance with a speed of 20 km `h^(-1)` and second `1 /3`and the last part with a speed of 60 km `h^(1)` The average speed of the car is:

Options

A. 55 km `h^(-1)`
B. 37.3km `h^(-1)`
C. 30km `h^(-1)`
D. 45km `h^(-1)`

Answer

c

Explanation

Using `(3)/(V_(av))=(1)/(v_(1))+(1)/(V_2)+(1)/(V_3)`
gives `v_(av) =30 km h^(-1)`