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91. A soldier fired two bullets at an interval of 335 seconds moving at a uniform speed V1. A terrorist who was running ahead of the soldier in same direction, hears the two shots at an interval of 330 seconds. If the speed of sound is 1188 km/h, then who is the faster and how much?

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Solution:
Speed of soundRelative speed of soldier and terrorist=         Time takenDifference in time
1188S=3305
Soldier = 18 km/h
92. A coolie standing on a railway platform observe that a train going in one direction takes 4 second to pass him. Another train of same length going in opposite direction takes 5 seconds to pass him. The time taken (in seconds) by two train to cross each other will be:

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Solution:
Let length of each train be X m, then
S1=X4andS2=X5Required time to cross each other,=2XX4+X5=409seconds
93. A dog start chasing to a cat 2 hour later. It takes 2 hours to dog to catch the cat. If the speed of the dog is 30 km/h. what is the speed of cat?

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Solution:
Let speed of the cat be S km/h.
Time taken = Distanced advancedRelative speed
2 = 2×S30S
S = 15 km/h
94. A car traveled first 36 km at 6 km/h faster than the usual speed, but it returned the same distance at 6 km/h slower than usual speed. I the total time taken by car is 8 hours, for how many hours does it traveled at the faster speed ?

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Solution:
Let the original speed be S then,
Total time taken,
36S6+36S+6    = 8 hours
On solving the equation, we get
S = 12, -3
Then possible value of S = 12 km/h.
Thus, time taken by car at faster speed = 3612+6  = 2 hours
95. Roorkee express normally reaches its destination at 50 km/h in 30 hours. Find the speed at which it travels to reduce the time by 10 hours?

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Solution:
let required speed be S km/h
50 × 30 = S × 20
S = 75 km/h
96. A train 350 m long is running at the speed of 36 km/h. If it crosses a tunnel in 1 minute, the length of the tunnel in metres:

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Solution:
Let the length of the tunnel be x m
Time = Length of train+Length of tunnelSpeed
60 = 350+x10
Speed=36×518=10m/sec
x = 250 meters
Therefore length of tunnel is 250 meters
97. If a 250 m long train crosses a platform of same length as that of the train in 25 seconds, then the speed of the train is:

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Solution:
Speed of train
= length of the train+length of platformTime
= 250+25025
= 20 m/sec
= 72 km/h
98. A postman goes with a speed of 36 km/h what is the speed of postman in m/s?

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Solution:
Speed = 36 km/h = 36×518  = 10 m/s
99. Sabarmati express takes 18 seconds to pass completely through a station 162 m long and 15 seconds through another station 120 m long. The length of the train is :

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Solution:
Let length of the train be x m
Speed of train,
x+16218=x+12015
x = 90 m
100. If two incorrect watches are set at 12:00 noon at correct time, when will both watches show the correct time for the first time given that the first watch gains 1 min in one hour and second watch looses 4 min in two hours.

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Solution:
First watch:
It shows correct time when it creates difference of 12 hours.
So, to create difference of 12 hour, time required = 60×1224   = 30 days

Second watch:
It shows correct time when it creates difference of 12 hours.
So, to create difference of 12 hour, time required = 30×1224   = 15 days
Now, LCM of 30 and 15 gives the time when they show correct time together. Thus, required time = 30 days, at same time.