Question

A $150$ metres long train crosses a man walking at the speed of $6$ km/hr in the opposite direction in $6$ seconds. The speed of the train in km/hr is ___________.

• A. $66$
• B. $84$
• C. $96$
• D. $106$

Answer 1

The correct option is B $84$

Let the speed of the train is $u$ km/hr

Then relative speed of train and man will be $u+6$ km/hr

It crosses a man in $6$ sec.

So, distance traveled $=150$ m (length of train)

$=0.15$ km,

time $=6$ sec $=\frac{6}{60\times 60}$ hr

$=\frac{1}{600}$ hr

So, speed will be $0.15\times 600$ $=90$ km/hr

$\Rightarrow 90=u+6$

$\Rightarrow u=84$ km/hr