Question

A train passes two persons walking in the same direction at a speed of $3$ km/hr and $5$ km/hr respectively in $10$ seconds and $11$ seconds. The speed of the train is

• A. $28$ km/hr
• B. $27$ km/hr
• C. $25$ km/hr
• D. $24$ km/hr

Answer 1

The correct option is C $25$ km/hr

Distance covered by the first person in $10$ seconds $=$ $[(3\times \frac{5}{18})\times 10]m=\frac{25}{3}m$
Distance covered by the second person in $11$ seconds $=$ $[(5\times \frac{5}{18})\times 11]m=\frac{275}{18}m$
$\therefore$ The train travels a distance $=$ $\frac{275}{18}-\frac{25}{3}=\frac{125}{18}m$ in $(11-10)=1$ second.
$\therefore$ Speed of the train $=$ $(\frac{125}{18}\times \frac{18}{5})$ km/hr $=25$ km/hr.