Speed, Time and Distance


  1. A person goes from one point to another point with a speed of 5 km/h and comes back to starting point with a speed of 3 km/h. Find the average speed for the whole journey.?
    1. 4.5 km/h
    2. 4 km/h
    3. 4. 25 km/h
    4. 3. 75 km/h

  1. View Hint View Answer Discuss in Forum

    Average speed = 2AB/(A + B)
    = 2 x 5 x 3/(5 + 3)

    Correct Option: D

    Average speed = 2AB/(A + B)
    = 2 x 5 x 3/(5 + 3)
    = 30/8
    = 3.75 km/h


  1. A train covers a distance in 1 h 40 min, if it runs at a speed of 96 km/h on an average. Find the speed at which the train must run reduce the time of journey to 1 h 20 min.
    1. 120 km/h
    2. 90 km/h
    3. 144 km/h
    4. 150 km/h

  1. View Hint View Answer Discuss in Forum

    Distance= Speed x Time = 96 x (100/60) = 160 km
    New time = 80/60 h = 4/3 h

    Correct Option: A

    Distance= Speed x Time = 96 x (100/60) = 160 km
    New time = 80/60 h = 4/3 h
    New speed = 160 x 3/4 = 40 x 3 =120 km/h



  1. The average speed of a car is 75 km/h. The driver first decrease its average speed by 40% and then increase it by 50%. What is the new average speed now ?
    1. 67.5 km
    2. 60 km
    3. 90 km
    4. 60.5 km

  1. View Hint View Answer Discuss in Forum

    Required average speed = 75 x {(100 - 40)/100} x {(100 + 50)/100}

    Correct Option: A

    Required average speed = 75 x {(100 - 40)/100} x {(100 + 50)/100}
    = 75 x 3/5 x 3/2
    = 67.5 km/h


  1. A train running at the speed of 72 km/hr passes a tunnel completely in 3 minutes. While inside the tunnel, it meets another
    train of
    3
    of its length coming from opposite
    4
    direction at the speed of 90km/hr and passes it completely in
    3
    1
    seconds. Find the length of the tunnel.
    2
    1. 3510 metre
    2. 3500 metre
    3. 3400 metre
    4. 3600 metre

  1. View Hint View Answer Discuss in Forum

    Trains are running in opposite directions.
    ∴  Relative speed = 72 + 90
    = 162 kmph

    = 162 ×
    5
    = 45 m/sec
    18

    Let the length of the first train be = x metre.
    ∴  Length of the second train
    =
    3
    x meter.
    4

    Now,
    distance travelled in 3
    1
    seconds at 45 m/sec.
    2

    = 45 ×
    7
    =
    315
    metre
    22

    This distance is equal to sum of the lengths of trains.
    ∴  x +
    3x
    =
    315
    42

    ⇒ 
    4x + 3x
    =
    315
    42

    ⇒ 
    7x
    =
    315
    42

    ⇒  x =
    315
    ×
    4
    = 90
    27

    Hence, the length of the first train = 90 metre.
    Speed of first train = 72 kmph
    = 72 ×
    5
    = 20 m/sec
    18

    Time taken by the first train to cross the tunnel
    = 3 minutes = 180 seconds
    ∴  Distance covered by it in 180 seconds
    = 180 × 20 = 3600 metre
    ∴  Length of (first train + tunnel) = 3600 metre
    ∴  Length of tunnel
    = 3600 – 90 = 3510 metre

    Correct Option: A

    Trains are running in opposite directions.
    ∴  Relative speed = 72 + 90
    = 162 kmph

    = 162 ×
    5
    = 45 m/sec
    18

    Let the length of the first train be = x metre.
    ∴  Length of the second train
    =
    3
    x meter.
    4

    Now,
    distance travelled in 3
    1
    seconds at 45 m/sec.
    2

    = 45 ×
    7
    =
    315
    metre
    22

    This distance is equal to sum of the lengths of trains.
    ∴  x +
    3x
    =
    315
    42

    ⇒ 
    4x + 3x
    =
    315
    42

    ⇒ 
    7x
    =
    315
    42

    ⇒  x =
    315
    ×
    4
    = 90
    27

    Hence, the length of the first train = 90 metre.
    Speed of first train = 72 kmph
    = 72 ×
    5
    = 20 m/sec
    18

    Time taken by the first train to cross the tunnel
    = 3 minutes = 180 seconds
    ∴  Distance covered by it in 180 seconds
    = 180 × 20 = 3600 metre
    ∴  Length of (first train + tunnel) = 3600 metre
    ∴  Length of tunnel
    = 3600 – 90 = 3510 metre



  1. In a one-kilometre race, A beats B by 15 seconds and B beats C by 15 seconds. If C is 100 metres away from the finishing mark, when B has reached it, find the speed of A.
    1. 9.5 m/sec.
    2. 9 m/sec.
    3. 8 m/sec.
    4. 8.3 m/sec

  1. View Hint View Answer Discuss in Forum

    Let B take x seconds to run 1000 m.
    ∴  Time taken by C
    = (x + 15) seconds

    ∴ 
    x
    =
    900
    =
    9
    x + 15100010

    ⇒  10x = 9x + 135
    ⇒  x = 135 seconds
    Now in a one kilometre race, A beats B by 15 seconds.
    It means A covers 1000 m in
    135 – 15 = 120 seconds
    ∴  Speed of A =
    1000
    =
    25
    m/sec
    1203

    = 8.3 m/sec.

    Correct Option: D

    Let B take x seconds to run 1000 m.
    ∴  Time taken by C
    = (x + 15) seconds

    ∴ 
    x
    =
    900
    =
    9
    x + 15100010

    ⇒  10x = 9x + 135
    ⇒  x = 135 seconds
    Now in a one kilometre race, A beats B by 15 seconds.
    It means A covers 1000 m in
    135 – 15 = 120 seconds
    ∴  Speed of A =
    1000
    =
    25
    m/sec
    1203

    = 8.3 m/sec.