SPEED, TIME AND DISTANCE (CDS)

Total Questions: 54

21. A 225 m long train is running at a speed of 30 km / hour. How much time does it take to cross a man running at 3 km / hour in the same direction? [2017 (I) Morning Shift ]

Correct Answer: (b) 30 s
Solution:We have,

22. A theif is spotted by a policeman from a distance of 100 m. When the policeman starts the chase, the theif also starts running. If the speed of the theif is 8 km / h and that of the policeman is 10 km/h, then how far will the theif have to run before he is overtaken? [2017 (I) Morning Shift ]

Correct Answer: (c) 400 m
Solution:Given,


23. Two men, A and B run a 4 km race on a course 0.25 km round. If their speeds are in the ratio 5 : 4, how often does the winner pass the another? [2016 (II) Evening Shift]

Correct Answer: (c) Thrice
Solution:When A completes 5 rounds, B completes 4 rounds

24. When the speed of a train is increased by 20%, it takes 20 min less to cover the same distance. What is the time taken to cover the same distance with the original speed? [2016 (II) Evening Shift]

Correct Answer: (b) 120 min
Solution:Let the distance = x km, original

25. A person can row downstream 20 km in 2h and upstream 4 km in 2 h. What is the speed of the current? [2016 (II) Evening Shift]

Correct Answer: (d) 4 km/h
Solution:


26. A motorist travels to a place 150 km away at an average speed of 50 km/h and returns at 30 km/h. What is the average speed for the whole journey? [2016 (II) Evening Shift]

Correct Answer: (c) 37.5 km/h
Solution:Total distance travelled by motorist = 150 + 150 = 300 km.

27. A train is travelling at 48 km/h completely crosses another train having half its length and travelling in opposite direction at 42 km/h in 12s. It also passes a railway platform in 45s. What is the length of the platform? [2016 (II) Evening Shift]

Correct Answer: (b) 400 m
Solution:Let the length of the train bel, then length of train travelling in opposite direction is l/2. Relative speed of train = (48 + 42) = 90 km/h

28. The speeds of three cars are in the ratio 2 : 3 : 4. What is the ratio between the times taken by these cars to travel the same distance? [2016 (II) Evening Shift]

Correct Answer: (d) 6 : 4 : 3
Solution:Let the speed of three cars be2x, 3x and 4x respectively.

29. A bike consumes 20 mL of petrol per km, if it is driven at a speed in the range of 25-50 km/h and consumes 40 mL of petrol per kilometre at any other speed. How much petrol is consumed by the bike in travelling a distance of 50 km, if the bike is driven at a speed of 40 km/h for the first 10 km, at a speed of 60 km/h for the next 30 km and at a speed of 30 km/h for the last 10 km? [2016 (I) Morning Shift ]

Correct Answer: (d) 1.6 L
Solution:Petrol consumed by the bike

30. A passenger train takes 1 h less for a journey of 120 km, if its speed is increased by 10 km/h from its usual speed. What is its usual speed? [2016 (I) Morning Shift ]

Correct Answer: (d) 30 km/h
Solution:Let the usual speed of train be x km/h.