It takes 10 seconds and 15 seconds for two trains of similar length to cross a telegraph post. If each train is 120 metres long, how long will it take for them to cross in the opposite direction (in seconds)?
A. 10
B. 12
C. 15
D. 20
Answer:B
It takes 10 seconds and 15 seconds for two trains of similar length to cross a telegraph post. If each train is 120 metres long, how long will it take for them to cross in the opposite direction (in seconds)?
A. 10 B. 12 C. 15 D. 20
Explanation: The first train's speed is ( 120/10 ) m/sec, or 12 m/sec.The second train's speed is ( 120/15 ) m/sec, or 8 m/sec.(12 + 8) = 20 m/sec relative speedAs a result, the required time is [ (120 + 120)/20 ].12 seconds equals sec.