Question

A train overtakes two persons walking along a railway track. The first person walks at 9 km/hr and the other walks at 10.8 km/hr. The train needs 16.8 and 17 seconds respectively to overtake them. What is the speed of the train if both the persons are walking in the same direction as the train?

• A. 108 kmph
• B. 144 kmph
• C. 162 kmph
• D. 180 kmph

Answer 1

The correct option is C

162 kmph

Let x is the length of the train in meter and y is its speed in kmph.

$\frac{x}{16.8}=(y-9)\times \frac{5}{18}$ --- (1)

$\frac{x}{17}=(y-10.8)\times \frac{5}{18}$ --- (2)

Dividing 1 by 2

$\frac{17}{16.8}=\frac{y-9}{y-10.8}$

=> 16.8y - 16.8 $\times$ 9 = 17y -- 17 $\times$ 10.8

$\Rightarrow$ 0.2y = 17 $\times$ 10.8 - 16.8 $\times$ 9

=> 0.2y = 183.6 - 151.2 = 32.4

=> y = 162 kmph