## Speed, Time and Distance

#### Speed, Time and Distance

1. Two donkeys are standing 400 metres apart. First donkey can run at a speed of 3 m/sec and the second can run at 2 m/sec. If two donkeys run towards each other after how much time (in seconds) will they bump into each other?
1. 60
2. 80
3. 400
4. 40

1. Distance between both donkeys = 400 metre.
Relative speed = (3 + 2) m./sec. = 5 m./sec.

 ∴  Required time = Distance Relative speed

 = 400 = 80 seconds 5

##### Correct Option: B

Distance between both donkeys = 400 metre.
Relative speed = (3 + 2) m./sec. = 5 m./sec.

 ∴  Required time = Distance Relative speed

 = 400 = 80 seconds 5

1. A man travels for 14 hours 40 minutes. He covers half of the journey by train at the rate of 60 km/hr and rest half by road at the rate of 50 km/hr. The distance travelled by him is :
1. 720 km
2. 800 km
3. 960 km
4. 1000 km

1. Let total distance covered be 2x km.
Total time = 14 hours 40 minutes

 = 14 40 hours = 14 2 hours 60 3

 = 44 hours 3

 Time = Distance Speed

According to the question,
 x + x = 44 60 50 3

 ∴ 5x + 6x = 44 300 3

 ⇒ 11x = 44 300 3

 ⇒  x = 44 × 300 = 400 3 11

∴  Total distance
= 2x = 2 × 400 = 800 km

##### Correct Option: B

Let total distance covered be 2x km.
Total time = 14 hours 40 minutes

 = 14 40 hours = 14 2 hours 60 3

 = 44 hours 3

 Time = Distance Speed

According to the question,
 x + x = 44 60 50 3

 ∴ 5x + 6x = 44 300 3

 ⇒ 11x = 44 300 3

 ⇒  x = 44 × 300 = 400 3 11

∴  Total distance
= 2x = 2 × 400 = 800 km

1. Sound travels 330 metre in a second.When the sound follows the flash of lightning after 10 seconds the thunder cloud will be at a distance of :
1. 1300 metre
2. 2000 metre
3. 3650 metre
4. 3300 metre

1. Distance = Speed × Time
= 330 × 10 = 3300 metre

##### Correct Option: D

Distance = Speed × Time
= 330 × 10 = 3300 metre

1. A man travelled a distance of 61 km. in 9 hours, partly by walking at the speed of 4 km./hr. and partly on bicycle at the speed of 9 km./hr. The distance covered by walking is
1. 16 km.
2. 12 km.
3. 15 km.
4. 17 km.

1. Let the distance covered on foot be x km.
∴  Distance covered on cycle = (61 – x) km.

 Time = Distance Speed

 ∴ x + 61 − x = 9 4 9

 ⇒ x − x = 9 − 61 4 9 9

 ⇒ 9x − 4x = 81 − 61 36 9

 ⇒ 5x = 20 36 9

 ⇒   x = 20 × 36 = 16 km. 9 5

##### Correct Option: A

Let the distance covered on foot be x km.
∴  Distance covered on cycle = (61 – x) km.

 Time = Distance Speed

 ∴ x + 61 − x = 9 4 9

 ⇒ x − x = 9 − 61 4 9 9

 ⇒ 9x − 4x = 81 − 61 36 9

 ⇒ 5x = 20 36 9

 ⇒   x = 20 × 36 = 16 km. 9 5

1. A farmer travelled a distance of 61 km in 9 hours. He travelled partly on foot at a speed of 4 km/hour and partly on bicycle at a speed of 9 km/hour. The distance travelled on foot is :
1. 14 km.
2. 16 km.
3. 20 km.
4. 18 km.

1. Length of journey on foot = x km. (let).
∴  Length of journey on cycle = (61 – x ) km.
According to the question,

 Time = Distance Speed

 ∴ x + 61 − x = 9 4 9

 ⇒ 9x + 244 − 4x = 9 36

⇒  5x + 244 = 36 × 9 = 324
⇒  5x = 324 – 244 = 80
 ⇒  x = 80 = 16 km 5

##### Correct Option: B

Length of journey on foot = x km. (let).
∴  Length of journey on cycle = (61 – x ) km.
According to the question,

 Time = Distance Speed

 ∴ x + 61 − x = 9 4 9

 ⇒ 9x + 244 − 4x = 9 36

⇒  5x + 244 = 36 × 9 = 324
⇒  5x = 324 – 244 = 80
 ⇒  x = 80 = 16 km 5