Question

Two trains each $100$ m long moving in opposite directions cross each other in $8$ seconds. If one is moving twice as faster as the other, then the speed of the faster train is

• A. $30$ km/hr
• B. $45$ km/hr
• C. $60$ km/hr
• D. $75$ km/hr

Answer 1

The correct option is C $60$ km/hr

Let the speeds of the two trains be $x$ m/s and $2x$ m/s respectively.
Since both he trains are moving in opposite directions, their relative speed $=(x+2x)$ m/s $=3x$ m/s.
Given, $\frac{100m+100m}{3x}=8$

$\Rightarrow x=\frac{200}{24}$ m/s $=(\frac{200}{24}\times \frac{18}{5})$ km/hr $=30$ km/hr
$\therefore$ Speed of the faster train $=60$ km/hr.