Question

Two trains of length 150 m and 170 m respectively are running at the speed of 40 km/hr and 32 km/hr on parallel tracks in opposite directions. Find the time taken for them to cross each other.

• A. 15 s
• B. 12 s
• C. 16 s
• D. 1 s

Answer 1

The correct option is C

16 s

Given,

Speed of train1 $S1$ = 40 km/hr
Length of train 1 = 150m

Speed of train2 $S2$ = 32 km/hr
Length of train 2 = 170m

Relative speed of train $=$ $(S1+S2)=(32+40)=72\text{km/hr}$

Converting it into m/s,$72\times \frac{5}{18}=20\text{m/s}$

Time taken by the two trains to cross each other
$=\frac{\text{Sum of the lengths of the trains}}{\text{Relative speed of the trains}}=\frac{150+170}{20}=\frac{320}{20}=16\text{s}$