Subject: General Aptitude · Chapter: Problems on Trains · Exam: 2003 · Marks: · Difficulty:
A moving train, 66 metres long, overtakes another train 88 metres long, moving in the same direction, in 0.168 minutes. If the second train is moving at 30 km per hour, at what speed is the first train moving?
Answer
Answer (as printed):
Explanation
Let the speed of the first train be $x$ km/hr. Then, sum of lengths of trains $=(66+88)$ m $=154$ m. Relative speed of two trains $=(x-30)$ kmph $=\left[(x-30) \times \frac{5}{18}\right]$ m/sec. $$\therefore \quad \frac{154}{(x-30) \times \frac{5}{18}}=0.168 \times 60 \Leftrightarrow 5(x-30)=\frac{154 \times 18}{10.08}=275 \Leftrightarrow x-30=55 \Leftrightarrow x=85.$$ Hence, speed of the first train $=85$ km/hr.
Explanation as extracted from the printed page; notation may be imperfect.