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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