Two trains each 100 m long moving in opposite directions cross each other in 8 seconds. If one is moving twice as fast the other then the speed of the faster train is:
30 km/hr
45 km/hr
60 km/hr
75 km/hr
Explanation:
Let the speed of the slower train be $ x $ m/sec.
Then, speed of the faster train = 2$ x $ m/sec.
Relative speed = $\left( x + 2 x\right)$ m/sec = 3$ x $ m/sec.
| $\therefore \dfrac{(100 + 100)}{8} $= 3$ x $ |
$\Rightarrow$ 24$ x $ = 200
| $\Rightarrow x $ =$ \dfrac{25}{3} $. |
| So, speed of the faster train =$ \dfrac{50}{3} $m/sec |
| =$ \left(\dfrac{50}{3} \times\dfrac{18}{5} \right) $km/hr |
= 60 km/hr.