A train 180 m. long moving at the speed of 20 m./sec. over takes a man moving at a speed of 10 m./sec. in the same direction. The train passes the man in - एक 180 मी. लम्बी रेलगाड़ी 20 मी./से. की चाल से एक व्यक्ति को जोकि समान दिशा में 10 मी./सेकेण्ड की चाल से चल रहा है, पार करती है। रेलगाड़ी व्यक्ति को कितने समय में पार करती है-
-
9 seconds
-
18 seconds
-
13 seconds
-
27 seconds
B
Correct answer
Explanation
When a train overtakes a person moving in the same direction, use relative speed. The train's speed minus the person's speed gives relative speed: 20 - 10 = 10 m/s. The train must cover its own length (180m) at this relative speed. Time = Distance / Speed = 180 / 10 = 18 seconds. Option A (9s) would be the result if you used 20 m/s without subtracting the man's speed. Option D (27s) might come from adding the speeds incorrectly.