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 distance at speed v. The average speed is $48 \,km/h$. The value of $v$ is

• A. 56 km/h
• B. 60 km/h
• C. 50 km/h
• D. 48 km/h

Answer 1

Answer: (B)

Given, Distance $=200 m$, Speed $=40 km / h$ Average speed $=48 km / h$
$ 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=60 km / h $