Speed, Time and Distance
 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 ?

View Hint View Answer Discuss in Forum
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, S_{1} = 40, t_{1} = 9
S_{2} = 60, t_{2} = ?
S_{1}t_{1} = S_{2}t_{2}
40 × 9 = 60 × t_{2}t_{2} = 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, S_{1} = 40, t_{1} = 9
S_{2} = 60, t_{2} = ?
S_{1}t_{1} = S_{2}t_{2}
40 × 9 = 60 × t_{2}t_{2} = 4 × 9 = 6 hours. 6
 An athlete runs 200 metres race in 24 seconds. His speed (in km/hr) is :

View Hint View Answer Discuss in Forum
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
 A car goes 10 metres in a second. Find its speed in km/hour.

View Hint View Answer Discuss in Forum
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
 A man crosses a road 250 metres wide in 75 seconds. His speed in km/hr is :

View Hint View Answer Discuss in Forum
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.
 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

View Hint View Answer Discuss in Forum
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 = 4Average 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 = 4Average speed = 2xy x + y = 2 × 25 × 4 = 200 25 + 4 29 Total Distance = 200 × 5 4 29 5 = 200 × 29 = 40 km 29 5