11. Two goods train each 500 m long are running in opposite directions on parallel tracks.Their speeds are 45 km/hr and 30 km/hr respectively.Find the time taken by the slower train to pass the driver of the faster one.

A. 12 sec B. 24 sec C. 48 sec D. 60 sec

Answer Answer: Option C Explanation: Relative speed =(45+30) km /hr =(75*5/18) m/sec =(125/6)m/sec
Distance covered = (500+500) m = 1000m
Required time =(1000*6/125) sec = 48 sec

12. Train P overtakes train Q double its length and traveling at half of speed of train P in 36 seconds. Train P crosses train R going in the opposite direction at double its speed in 8 seconds. If the speed of train P is 72 km/ph then the length of train R is?

A. 330 m B. 360 m C. 390 m D. 420 m

Answer Answer: Option B Explanation: For Train P
length = L, Speed = 72 kmph
For train Q
length = 2L, Speed = 36 kmph
(L + 2L)/(72 - 36)X5/18
L= 120 meter
For train R
Speed = 2 X 72 = 144 kmph
& length = x meter
(120 + x) / (144 + 72)X5/18 = 8
x = 360 meter

13. The length of train and that of platform are equal. If with a speed of 90 km/hr, the train crosses the platform in one minute, then the length of the train (in meters) is?

A. 500 B. 600 C. 750 D. 900

Answer Answer: Option C Explanation: Speed = (90*5/18) m/sec =25 m/sec; time 1 min. = 60 sec.
Let the length of the train and that of the platform be x meters.
then, 2x/60 =25 <=> x = 25*60/2 =750.

14. The length of the bridge, which a train 130 meters long and traveling at 45 km/hr can cross in 30 seconds, is?

A. 245 m B. 200 m C. 225 m D. 250 m

Answer Answer: Option A Explanation: Speed =(45*5/18) m/sec = (25/2) m/sec; time = 30 sec.
Let the length of bridge be x meters.
Then, 130+x/30 = 25/2 <=> 2(130+x) =750 <=> x = 245 m.