Question

A passenger train of length $60m$ travels at a speed of $80km/hr$. Another freight train of length $120m$ travels at a speed of $30km/hr$.The ratio of times taken by the passenger train to completely cross the freight train when: (i) they are moving in the same direction, and (ii) in the opposite directions is

• A. $\frac{3}{2}$
• B. $\frac{11}{5}$
• C. $\frac{5}{2}$
  
• D. $\frac{25}{11}$

Answer 1

The correct option is B $\frac{11}{5}$

When trains are moving in the same direction
$t_1=\frac{L_1+L_2}{v-u}=\frac{L}{80-30}=\frac{L}{50}\dots \left(i\right)$
When trains are moving in the opposite direction
$t_2=\frac{L_1+L_2}{v+u}=\frac{L}{80-30}=\frac{L}{110}\dots \left(i\right)$
From (i) and (ii),
$\frac{t_1}{t_2}=\frac{11}{5}$