## Speed, Time and Distance

#### Speed, Time and Distance

1. 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 :
1. 80 m
2. 90 m
3. 200 m
4. 150 m

1. 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

1. 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 :
1. 500
2. 600
3. 750
4. 900

1. 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

##### Correct 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

1. 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
1. 35 km.
2. 21 km.
3. 9 km.
4. 12 km.

1. 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

1. 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 :
1. 0.33 km.
2. 3.3 km.
3. 33 km.
4. 33.3 km.

1. 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

1. 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?
1. 65 km/h
2. 70 km/h
3. 75 km/h
4. 80 km/h

1. 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