Question

A train $150m$ long passes a pole in $15s$ time, and it takes $8s$ to pass another train of the same length travelling in opposite direction. What is the speed of the second train?

• A. 60 km/hr
• B. 66 km/hr
• C. 72 km/hr
• D. 99 km/hr

Answer 1

Answer: (D)

Speed of first train $=\left(\frac{150}{15}\right)\frac{m}{sec}=10\frac{m}{sec}$
Let the speed of second train be x m/sec.
Relative speed $=\left(10+x\right)\frac{m}{sec}$ .
$\therefore$ $\frac{300}{10+x}=8\iff 300=80+8x\iff x=\frac{220}{5}=\frac{55}{2}\frac{m}{sec}$ .
So, speed of second train $=\left(\frac{55}{2}\times \frac{18}{5}\right)kmph=99kmph$ .