Question

Two trains are running at $40km/hr$ and $20km/hr$ respectively in the same direction. The fast train completely passes a man sitting in the slow train in $5$ seconds. The length of the fast train is

• A. $23\frac{2}{9}m$
• B. $27m$
• C. $27\frac{7}{9}m$
• D. $23m$

Answer 1

The correct option is C $27\frac{7}{9}m$

Relative speed $=(40-20)=20km/hr$
[$\because$ train are moving in same direction]
Relative speed $=\frac{\text{Length of the faster train}}{Time}$
$20\times \frac{5}{18}=\frac{\text{Length of the faster train}}{5}$
Length of the faster train $=\frac{20\times 5\times 5}{18}=\frac{250}{9}=27\frac{7}{9}m$.