## Speed, Time and Distance

#### Speed, Time and Distance

1. A motorist travels to a place 150 km away at an average speed of 50 km/hr and returns at 30 km/hr. His average speed for the whole journey in km/hr is
1. 37.5
2. 37
3. 35
4. 40

1.  Average speed of whole journey = 2xy kmph x + y

 = 2 × 50 × 30 kmph 50 + 30

 = 2 × 50 × 30 = 37.5 kmph 80

##### Correct Option: A

 Average speed of whole journey = 2xy kmph x + y

 = 2 × 50 × 30 kmph 50 + 30

 = 2 × 50 × 30 = 37.5 kmph 80

1. A train runs from Howrah to Bandel at an average speed of 20 km/hr and returns at an average speed of 30 km/hr. The average speed (in km/hr) of the train in the whole journey is
1. 20
2. 22.5
3. 24
4. 25

1.  Average speed = 2xy kmph x + y

 = 2 × 20 × 30 20 + 30

 = 2 × 20 × 30 = 24 kmph 50

##### Correct Option: C

 Average speed = 2xy kmph x + y

 = 2 × 20 × 30 20 + 30

 = 2 × 20 × 30 = 24 kmph 50

1. A and B are 20 km apart. A can walk at an average speed of 4 km/hour and B at 6 km/hr. If they start walking towards each other at 7 a.m., when they will meet ?
1. 8.00 a.m.
2. 8.30 a.m.
3. 9.00 a.m.
4. 10.00 a.m.

1. If A and B meet after t hours, then
4 t + 6 t = 20
⇒  10 t = 20

 ⇒  t = 20 = 2 hours. 10

Hence, both will meet at 9 a.m.

##### Correct Option: C

If A and B meet after t hours, then
4 t + 6 t = 20
⇒  10 t = 20

 ⇒  t = 20 = 2 hours. 10

Hence, both will meet at 9 a.m.

1. A train goes from Ballygunge to Sealdah at an average speed of 20 km/hour and comes back at an average speed of 30 km/hour. The average speed of the train for the whole journey is
1. 27 km/hr
2. 26 km/hr
3. 25 km/hr
4. 24 km/hr

1.  Required average speed = 2 × 30 × 20 30 + 20

[∵  Distance covered is same]
 = 2 × 30 × 20 = 24 kmph 50

##### Correct Option: D

 Required average speed = 2 × 30 × 20 30 + 20

[∵  Distance covered is same]
 = 2 × 30 × 20 = 24 kmph 50

1. On a journey across Kolkata, a taxi averages 50 km per hour for 50% of the distance, 40 km per hour for 40% of it and 20 km per hour for the remaining. The average speed (in km/hour) for the whole journey is :
1. 42
2. 40
3. 35
4. 45

1. Total distance = 100 km.

 Total time = 50 + 40 + 10 50 40 20

 = 1 + 1 + 1 = 5 hours 2 2

 ∴ Average speed = 100 × 2 = 40 kmph 5

##### Correct Option: B

Total distance = 100 km.

 Total time = 50 + 40 + 10 50 40 20

 = 1 + 1 + 1 = 5 hours 2 2

 ∴ Average speed = 100 × 2 = 40 kmph 5