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. View Hint View Answer Discuss in Forum

    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. View Hint View Answer Discuss in Forum

    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. View Hint View Answer Discuss in Forum

    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. View Hint View Answer Discuss in Forum

    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. View Hint View Answer Discuss in Forum

    Total distance = 100 km.

    Total time =
    50
    +
    40
    +
    10
    504020

    = 1 + 1 +
    1
    =
    5
    hours
    22

    ∴ Average speed =
    100 × 2
    = 40 kmph
    5

    Correct Option: B

    Total distance = 100 km.

    Total time =
    50
    +
    40
    +
    10
    504020

    = 1 + 1 +
    1
    =
    5
    hours
    22

    ∴ Average speed =
    100 × 2
    = 40 kmph
    5