1. A train leaves Delhi at 6 a.m and reaches chandigarh at 10 a.m. Another train leaves chandigarh at 8 a.m and reaches Delhi at 11.30 a.m. At what time do the two trains cross one another ?

1. 9.26 a.m

2. 9 a.m

3. 8.36 a.m

4. 8.56 a.m

5. 9.56 a.m

Answer & Explanation

Answer:- 4

Explanation :-

Let the total distance be x km

Therefore , the speed of 1st train = x / 4

The speed of 2nd train = x / 3.5

In 2 hours 1st train covers half of the total distance .

So remaining is only half of the total distance(ie x/2).

Let t be the time taken

Distance = Time * speed

t*x/4 + t*x/3.5 = x/2

t = 14/15 i.e. 56 min

Total time taken = 2 hrs + 56 min

Time they cross each other is 7:56am (5+2.56)

2. A passenger train takes two hours less for a journey of 300km if its speed is increased by 5km/hr from its normal speed. The normal speed is:

1.35 km/hr

2.50 km/hr

3.25 km/hr

4.30 km/hr

5.37Km/hr

Answer:- 3

Explanation :-

Let,s Suppose the normal speed of train = x km/hr

Increased speed = (x + 5) km/hr

(300/ x) – 2 = [300 / (x + 5)]
(300 – 2x) / x = 300 / (x + 5)

(300 – 2x) (x + 5) = 300x

300x – 2(x*x) +1500 -10x = 300

2(x^2) + 10x -1500 = 0

(x^2) + 5x – 750 = 0

x = 25 km/h

3. A thief steals a car and drives it at 15 km/hr. The theft has been discovered after one hour and the owner of the car sets off in another car at 25 km/hr. When will the owner overtake the thief from the starting point?

1.1 hr

2.1.5 hr

3.2 hr

4.2.5 hr

5. 3 hr

Answer & Explanation

Answer:- 2

Explanation :-

In 1 hour Distance covered by the thief = 15 km

Relative speed = (25−15) = 10 km/hr

Time Taken to cover this distance at a speed of 10 km/hr = 15/10 = 1.5 hr

4. A car travels first half distance between two places with a speed of 40 km/hr and rest of the half distance with a speed of 60 km/hr. The average speed of the car is:

1.48 km/hr

2.37 km/hr

3.44 km/hr

4.45 km/hr

5.42 Km/hr

Answer & Explanation

Answer:- 1

Explanation :-

Let the total distance covered = x km

Time = Distance / speed , Therefore

Time for First Half = (x/2) / 40

Time for Second Half = (x/2) / 60

Total Time = [(x/2) / 40] + [(x/2) / 60] = 5x/240

Average Speed = Total distance / Total Time

Average Speed = x / (5x/240)

Average Speed =48 km/h

5.Two identical trains A and B running in opposite direction at same speed take 2 min to cross each other completely. The number of bogies of A are increased from 12 to 16. How much more time would they now require to cross each other?

1.40 sec

2.50 sec

3.60 sec

4.20 sec

5.30 sec

Answer & Explanation

Answer:- 4

Explanation :-

Total initial bogies = 12+12 = 24

Additional bogies =16 −12 = 4

24 bogies take 2 minutes.

Time Taken by 4 bogies = (2/24) * 4 = 1/3 min = (1/3)*60 Sec = 20 Sec.