Speed, Time and Distance
 A train passes two bridges of lengths 800 m and 400 m in 100 seconds and 60 seconds
respectively. The length of the train is :

 80 m
 90 m
 200 m
 150 m

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When a train crosses a bridge it covers the distance equal to length of Bridge & its own length
Let the length of the train be = x∴ Speed of the train = x + 800 m/s 100
Since train passes the 800 m bridge in 100 seconds.
Again, train passes the 400 m bridge in 60 seconds.∴ 400 + x = 60 x + 800 100 ⇒ (400 + x) × 100 = 60 x + 800
⇒ 40000 + 100x
= 60x + 48000
⇒ 100x – 60x = 48000 – 40000
⇒ 40x = 8000∴ x = 8000 = 200m 40 Correct Option: C
When a train crosses a bridge it covers the distance equal to length of Bridge & its own length
Let the length of the train be = x∴ Speed of the train = x + 800 m/s 100
Since train passes the 800 m bridge in 100 seconds.
Again, train passes the 400 m bridge in 60 seconds.∴ 400 + x = 60 x + 800 100 ⇒ (400 + x) × 100 = 60 x + 800
⇒ 40000 + 100x
= 60x + 48000
⇒ 100x – 60x = 48000 – 40000
⇒ 40x = 8000∴ x = 8000 = 200m 40
 The length of a train and that of a 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 metres) is :

 500
 600
 750
 900

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Let the length of train be x metre
Speed = 90 km/hr= 90 × 5 metre/sec. 18
= 25 metre/sec.
∴ Distance covered in 60 sec.
= 25 × 60 = 1500 metres
Now, according to question,
2x = 1500
∴ x = 750 metreCorrect Option: C
Let the length of train be x metre
Speed = 90 km/hr= 90 × 5 metre/sec. 18
= 25 metre/sec.
∴ Distance covered in 60 sec.
= 25 × 60 = 1500 metres
Now, according to question,
2x = 1500
∴ x = 750 metre
 A man travels some distance at a speed of 12 km/hr and returns at a speed of 9 km/hr. If the total time taken by him is 2 hrs 20 minutes the distance is

 35 km.
 21 km.
 9 km.
 12 km.

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Let the required distance be x km.
Time = 2 hours 20 minutes 2 1 hours 3
According to the question,x + x = 7 12 9 3 ⇒ 3x + 4x = 7 36 3 ⇒ 7x = 7 36 3 ⇒ x = 7 × 36 = 12 km. 3 7 Correct Option: D
Let the required distance be x km.
Time = 2 hours 20 minutes 2 1 hours 3
According to the question,x + x = 7 12 9 3 ⇒ 3x + 4x = 7 36 3 ⇒ 7x = 7 36 3 ⇒ x = 7 × 36 = 12 km. 3 7
 Sound travels at 330 metre per second. The distance (in kilometre) of a thunder cloud when its sound follows the flash after 10 seconds is :

 0.33 km.
 3.3 km.
 33 km.
 33.3 km.

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Distance = Speed × Time
= 330 × 10 = 3300 metre= 3300 km. = 3.3 km. 1000 Correct Option: B
Distance = Speed × Time
= 330 × 10 = 3300 metre= 3300 km. = 3.3 km. 1000
 To cover a certain distance with a speed of 60 km/hr, a train takes 15 hours. If it covers the
same distance in 12 hours, what will be its speed?

 65 km/h
 70 km/h
 75 km/h
 80 km/h

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Distance covered by train in
15 hours = Speed × Time
= (60 × 15) km. = 900 km.
Required speed to cover 900 km.in 12 hours = 900 = 75 kmph 12 Correct Option: C
Distance covered by train in
15 hours = Speed × Time
= (60 × 15) km. = 900 km.
Required speed to cover 900 km.in 12 hours = 900 = 75 kmph 12