Question

A car covers the first half the distance between two places at 40 km/h another half at 60 km/h, the average speed of car

• A. 50 km/h
• B. 60 km/h
• C. 40 km/h
• D. 48 km/h

Answer 1

Answer: (D)

The correct option is B 48 km/h
Letx consider, $x=$ total distance covered by the car,

Time taken to complete the half distance with velocity $v=40km/h$,

$t_1=\frac{x}{2\times 40}=\frac{x}{80}hr$. . . . .(1)

The time taken to complete another half distance with velocity $u=60km/h$

$t_2=\frac{x}{2\times 60}=\frac{x}{120}hr$

The total time taken, $t=t_1+t_2$

$t=\frac{x}{80}+\frac{x}{120}=\frac{x}{48}hr$

The average speed of the car,

$v_{avg}=\frac{x}{x/48}=48km/h$

The correct option is B.