18
Q:

# Two trains started at the same time, one from A to B and the other from B to A . If they arrived at B and A respectively 4 hours and 9 hours after they passed each other the ratio of the speeds of the two trains was

 A) 2:1 B) 3:2 C) 4:3 D) 5:4

Explanation:

Note : If two trains (or bodies) start at the same time from points A and B towards each other and after crossing they take a and b sec in reaching B and A respectively, then: (A's speed) : (B's speed) = (b : a)

Therefore, Ratio of the speeds of two trains = $\inline \sqrt{9}:\sqrt{4}$ = 3 : 2

Q:

Two trains are running at 40 km/hr and 20 km/hr respectively in the same direction. Fast train completely passes a man sitting in the slower train in 5 seconds. What is the length of the fast train?

 A) 27 7/9 mts B) 25 8/7 mts C) 21 1/4 mts D) 22 mts

Explanation:
 Relative speed = (40 - 20) km/hr = 20 x 5 m/sec = 50 m/sec. 18 9
 Length of faster train = 50 x 5 m = 250 m = 27 7 m. 9 9 9

1 20
Q:

A train is moving and crossing a man who is running on a  platform of 100 m at a speed of 8 kmph in the direction of the train, in 9 sec. If the speed of the train is 74 kmph. Find the length of the train ?

 A) 202 mts B) 188 mts C) 165 mts D) 156 mts

Explanation:

Let the length of the train = L mts

Relative speed of train and man = 74 - 8 = 66 kmph = 66 x 5/18 m/s

=> 66 x 5/18 = L/9

=> L = 165 mts.

9 139
Q:

A train travelling at 48 kmph crosses another train, having half its length and travelling in opposite direction at 42 kmph, in 12 sec. It also covers a bridge in 45 sec. Find the length of the bridge ?

 A) 250 mts B) 400 mts C) 320 mts D) 390 mts

Explanation:

Let the length of the 1st train = L mts

Speed of 1st train = 48 kmph

Now the length of the 2nd train = L/2 mts

Speed of 2nd train = 42 kmph

Let the length of the bridge = D mts

Distance = L + L/2 = 3L/2

Relative speed = 48 + 42 = 90 kmph = 90 x 5/18 = 25 m/s(opposite)

Time = 12 sec

=> 3L/2x25 = 12

=> L = 200 mts

Now it covers the bridge in 45 sec

=> distance = D + 200

Time = 45 sec

Speed = 48 x5/18 = 40/3 m/s

=> D + 200/(40/3) = 45

=> D = 600 - 200 = 400 mts

Hence, the length of the bridge = 400 mts.

5 211
Q:

The difference between the time taken by two trains to travel a distance of 350 km is 2 hours 20 minutes. If the difference between their speeds is 5 km/hr, what is the speed of faster train ?

 A) 36 kmph B) 30 kmph C) 34 kmph D) 40 kmph

Explanation:

Let the speed of the faster train be 'S' kmph

Then speed of the slower train will be '(S-5)' kmph

Time taken by faster train = 350/S hrs

Time taken by slower train = 350/(S-5) hrs

$\inline \fn_jvn \frac{350}{S-5}-\frac{350}{S}=2hrs20min=2\tfrac{1}{3}=\frac{7}{3}$

=> S = 30 km/hr.

5 304
Q:

Find the length of a train if it takes 10 seconds to cross a pole and double of this time to cross a platform of length 200 mts ?

 A) 180 mts B) 190 mts C) 200 mts D) 210 mts

Explanation:

Let the length of the train be 'L' mts

let the speed of the train be 'S' m/s

Given it crosses a pole in 10 sec=> L/S = 10 ......(1)
Given it takes 20 sec (double of pole) to cross a platform of length 200 mts

=> (L + 200)/S = 20

=> L/S + 200/S = 20

But from (1) L/S = 10

=> 200/S = 20 - 10

=> S = 20 m/s

Then, from (1)

=> L = 10 x 20 = 200 mts.

Hence, the length of the train = 200 mts.