Aptitude - Aptitude- Speed

OOPS, your answer is incorrect

Since, Two trains travel in opposite directions at 36 kmph and 45 kmph,
Relative speed = (36 + 45) km/hr = [81 * (5/18)] m/sec = [45/2] m/sec.

Length of train = [(45/2) * 8] m = 180 m.

OOPS, your answer is incorrect

Since, two trains are running at 40 km/hr and 20 km/hr respectively in the same direction,
Relative speed = (40-20) km/hr = [20 * (5/18)] m/sec = [50/9] m/sec.
ஃLength of faster train = [(50/9) * 5] m = 250/9 m = 27 7/9 m.

OOPS, your answer is incorrect

Let the length of the train be x metres.
Then, the train covers x metres in 8 seconds and (x + 180) metres in 20 seconds.
Length of the train = x/8 --- case(1)
Length of the train = x + 180/20 --- case(2)

Case(1) = Case(2)
By solving,
We get, Length of the train (x) = 120 m
Speed of the train = 120/8 = 15 m/s = 15 x (18/5) = 54 km/hr

OOPS, your answer is incorrect

Speed = Distance/time
Total distance travelled by the train = tunnel length + train length itself.

ஃTotal distance = 450 meters.
time= 40.5 sec.

Hence, Speed of the train = 450 / 40.5 = 11. 11 m/s
Converting to km/hr = 11.11 x (18/5) ≈40

OOPS, your answer is incorrect

Speed of the train = distance or length of train / time

Speed = 240 / 24 = 10 (m/s)

Please note that when a train crosses a pole, it crosses with the distance of itself.

So, the total distance will be equal to length of platform + length of train

Total distance = 240 + 650 = 890 meters.

Total time taken = distance / speed = 890 / 10 = 89 sec