Question

Two trains can run at a speed of $54$ km/hr and $36$ km/hr on a parallel tracks. When they are running in opposite directions they pass each other in $10$ s, when they move in the same direction a person sitting in the faster train crosses the other train in $30$ s. Find the length of the trains ( faster and slower respectively ).

• A. $100$ m and $150$ m
• B. $150$ m and $100$ m
• C. $150$ m each
• D. $100$ m each

Answer 1

The correct option is A $100$ m and $150$ m

when trains are running in same direction then relative relative speed $=54-36=18km/hr=(18\times \frac{5}{18})m/sec=5m/sec$

Time $=30s$

Length of the faster train$=5\times 30=150m$

When trains are running in opposite direction then relative speed $=54+36=90km/hr=(90\times \frac{5}{18})m/sec=25m/sec$

time$=10$ s

Length of the trains$=25\times 10=250m$

Length of the slower train$=250-150=100m$

Length of the trains are $100$ m and $150$ m.