Question

A car moves a distance of 200 m. It covers the first half of the distance at speed 40 km/h and the second half of the distance at speed v. If the average speed is 48 km/h, then the value of v is-

• A. 50 km/h
• B. 56 km/h
• C. 58 km/h
• D. 60 km/h

Answer 1

The correct option is D 60 km/h

Given, $Distance=200m,Speed=40km/h$ Average speed =$48km/h$

$48=\frac{200}{\frac{100}{40}+\frac{100}{v}}\Rightarrow \frac{1}{40}+\frac{1}{v}=\frac{1}{24}\Rightarrow v=\frac{120}{5-3}=\frac{120}{2}\Rightarrow =60km/h$