## Speed, Time and Distance

#### Speed, Time and Distance

1. A car travelling at a speed of 40 km/hour can complete a journey in 9 hours. How long will it take to travel the same distance at 60 km/hour ?

1. Total distance covered
= Speed × Time
= 40 × 9 = 360 km.
The required time at 60 kmph

 = 360 = 6 hours. 60

Second Method :
Using Rule 9,
Here, S1 = 40, t1 = 9
S2 = 60, t2 = ?
S1t1 = S2t2
40 × 9 = 60 × t2
 t2 = 4 × 9 = 6 hours. 6

##### Correct Option: A

Total distance covered
= Speed × Time
= 40 × 9 = 360 km.
The required time at 60 kmph

 = 360 = 6 hours. 60

Second Method :
Using Rule 9,
Here, S1 = 40, t1 = 9
S2 = 60, t2 = ?
S1t1 = S2t2
40 × 9 = 60 × t2
 t2 = 4 × 9 = 6 hours. 6

1. An athlete runs 200 metres race in 24 seconds. His speed (in km/hr) is :

1.  Speed = Distance Time

 = 200 m/s 24

 200 m/s = 10 × 18 = 30 km/hr. 24 24 5

 ∵   x m/s = 18 x km/hr 5

##### Correct Option: D

 Speed = Distance Time

 = 200 m/s 24

 200 m/s = 10 × 18 = 30 km/hr. 24 24 5

 ∵   x m/s = 18 x km/hr 5

1. A car goes 10 metres in a second. Find its speed in km/hour.

1. Speed of car = 10 m/sec.
Required speed in kmph

 = 10 × 18 = 36 km/hr 5

##### Correct Option: D

Speed of car = 10 m/sec.
Required speed in kmph

 = 10 × 18 = 36 km/hr 5

1. A man crosses a road 250 metres wide in 75 seconds. His speed in km/hr is :

1.  Speed = Distance = 250 75 3

 = 10 m/sec = 10 × 18 km/hr. 3 3 5

 ∵   1 m/s = 18 km/hr 5

= 2 × 6 km/hr. = 12 km/hr.

##### Correct Option: B

 Speed = Distance = 250 75 3

 = 10 m/sec = 10 × 18 km/hr. 3 3 5

 ∵   1 m/s = 18 km/hr 5

= 2 × 6 km/hr. = 12 km/hr.

1. A man travelled a certain distance by train at the rate of 25 kmph. and walked back at the
rate of 4 kmph. If the whole journey took 5 hours 48 minutes, the distance was

1. Let the distance be x km.
Total time = 5 hours 48 minutes

 = 5 + 48 = 5 + 4 hours 60 5

 = 29 hours 5

 ∴ x + x = 29 25 4 5

 ⇒ 4x + 25x = 29 100 5

⇒  5 × 29x = 29 × 100
 ⇒  x = 29 × 100 = 20 km. 5 × 29

Second Method :
Here, x = 25, y = 4
 Average speed = 2xy x + y

 = 2 × 25 × 4 = 200 25 + 4 29

 Total Distance = 200 × 5 4 29 5

 = 200 × 29 = 40 km 29 5

##### Correct Option: C

Let the distance be x km.
Total time = 5 hours 48 minutes

 = 5 + 48 = 5 + 4 hours 60 5

 = 29 hours 5

 ∴ x + x = 29 25 4 5

 ⇒ 4x + 25x = 29 100 5

⇒  5 × 29x = 29 × 100
 ⇒  x = 29 × 100 = 20 km. 5 × 29

Second Method :
Here, x = 25, y = 4
 Average speed = 2xy x + y

 = 2 × 25 × 4 = 200 25 + 4 29

 Total Distance = 200 × 5 4 29 5

 = 200 × 29 = 40 km 29 5