Problems on Trains ( 16 to 20 )

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Problems on Trains ( 16 to 20 ):


APTITUDE QUESTIONS (PROBLEMS ON TRAINS):

16. Two trains travel in opposite directions at 36 km/hr and 45 km/hr and a man sitting in slower train passes the f*er train in 8 seconds. The length of the f*er train is:

A)    80 m

B)    100 m

C)    120 m

D)    180 m

E)    None of these

View Answer

Answer: option D

Explanation:

Relative speed = (36 + 45) km/hr = (81*5 / 18) m/sec = (45/2) m/sec

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

 

17. Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds. What will be the speed of the f*er train if one is moving twice as f* the other?

A)    50 km/hr

B)    45 km/hr

C)    60 km/hr

D)    75 km/hr

E)    None of these

View Answer

Answer: option C

Explanation:

Let the speed of the slower train be x m/sec

Then, speed of the f*er train = 2x m/sec

Relative speed = (x + 2x) m/sec = 3x m/sec

∴ (100+100) / 8 = 3x <=> 24x = 200 <=> x = 25/3

So, speed of the faster train = 50/3 m/sec = (50/3 * 18/5)km/hr = 60 km/hr

 

18. A train 150 m long passes a km stone in 15 seconds and another train of the same length travelling in opposite direction in 8 seconds. The speed of the second train is:

A)    60 km/hr

B)    66 km/hr

C)    72 km/hr

D)    99 km/hr

E)    None of these

View Answer

Answer: option D

Explanation:

Let speed of first train be = (150/15) m/sec = 10 m/sec and speed of second train be x m/sec

Relative speed = (10 + x) m/sec

∴ 300 / (10+x) = 8 <=> 300 = 80 + 8x <=> 8x = 220 <=> x = 220/8 = 55/2 m/sec


So, speed of second train = (55/2 * 18/5) km/hr = 99 km/hr

 

19. Two trains, one form Delhi to Mumbai and the other from Mumbai to Delhi, start simultaneously. After they meet, the trains reach their destination after 4 hours and 9 hours respectively. The ratio of their speed is:

A)   2:3

B)   3:2

C)    6:7

D)    9:16

E)    None of these

View Answer

Answer: option B

Explanation:

Let the trains name be X and Y.

Then, (X’s speed) : (Y’s speed) = √y : x = 9 : 4 = 3:2

 

20. A speed of 14 metres per second is the same as:

A)    28 km/hr

B)    46.6 km/hr

C)    50.4 km/hr

D)    70 km/hr

E)    None of these

View Answer

Answer: option C

Explanation:

14 m/sec = (14 * 18/5) km/hr = 50.4 km/hr

 

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