Speed, Time and Distance


  1. A boy runs 20 km in 2.5 hours. How long will he take to run 32 km at double the previous speed ?
    1. 2 hours
    2. 2
      1
      hours
      2
    3. 4
      1
      hours
      2
    4. 5 hours

  1. View Hint View Answer Discuss in Forum

    The boy covers 20 km in 2.5 hours.

    ⇒ Speed =
    20
    = 8 km/hr.
    2.5

    New speed = 16 km/hr
    ∴ Time =
    32
    = 2 hours.
    16

    Correct Option: A

    The boy covers 20 km in 2.5 hours.

    ⇒ Speed =
    20
    = 8 km/hr.
    2.5

    New speed = 16 km/hr
    ∴ Time =
    32
    = 2 hours.
    16


  1. A boy goes to his school from his house at a speed of 3 km/hr and returns at a speed of 2 km/hr. If he takes 5 hours in going and coming, the distance between his house and school is :
    1. 6 km
    2. 5 km
    3. 5.5 km
    4. 6.5 km

  1. View Hint View Answer Discuss in Forum

    Let the required distance be x km.
    Then,

    x
    +
    x
    = 5
    32

    ⇒ 
    2x + 3x
    = 5
    6

    ⇒  5x = 6 × 5
    ∴  x =
    6 × 5
    = km
    5


    Second Method :
    Here, x = 3, y = 2
    Average Speed =
    2 × x × y
    x + y

    =
    2 × 3 × 2
    3 + 2

    =
    12
    km/hr
    5

    Total distance =
    12
    × 5 = 12km
    5

    ∴  Required distance =
    12
    = 6 km
    2

    Correct Option: A

    Let the required distance be x km.
    Then,

    x
    +
    x
    = 5
    32

    ⇒ 
    2x + 3x
    = 5
    6

    ⇒  5x = 6 × 5
    ∴  x =
    6 × 5
    = km
    5


    Second Method :
    Here, x = 3, y = 2
    Average Speed =
    2 × x × y
    x + y

    =
    2 × 3 × 2
    3 + 2

    =
    12
    km/hr
    5

    Total distance =
    12
    × 5 = 12km
    5

    ∴  Required distance =
    12
    = 6 km
    2



  1. 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
    1. 25 km
    2. 30 km
    3. 20 km
    4. 15 km

  1. View Hint View Answer Discuss in Forum

    Let the distance be x km.
    Total time = 5 hours 48 minutes

    = 5 +
    48
    = 5 +
    4
    hours
    605

    =
    29
    hours
    5

    ∴ 
    x
    +
    x
    =
    29
    2545

    ⇒ 
    4x + 25x
    =
    29
    1005

    ⇒  5 × 29x = 29 × 100
    ⇒  x =
    29 × 100
    = 20 km.
    5 × 29


    Second Method :
    Here, x = 25, y = 4
    Average speed =
    2xy
    x + y

    =
    2 × 25 × 4
    =
    200
    25 + 429

    Total Distance =
    200
    × 5
    4
    295

    =
    200
    ×
    29
    = 40 km
    295

    Correct Option: C

    Let the distance be x km.
    Total time = 5 hours 48 minutes

    = 5 +
    48
    = 5 +
    4
    hours
    605

    =
    29
    hours
    5

    ∴ 
    x
    +
    x
    =
    29
    2545

    ⇒ 
    4x + 25x
    =
    29
    1005

    ⇒  5 × 29x = 29 × 100
    ⇒  x =
    29 × 100
    = 20 km.
    5 × 29


    Second Method :
    Here, x = 25, y = 4
    Average speed =
    2xy
    x + y

    =
    2 × 25 × 4
    =
    200
    25 + 429

    Total Distance =
    200
    × 5
    4
    295

    =
    200
    ×
    29
    = 40 km
    295


  1. 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 ?
    1. 6 hours
    2. 3 hours
    3. 4 hours
    4. 4
      1
      hours
      2

  1. 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, S1 = 40, t1 = 9
    S2 = 60, t2 = ?
    S1t1 = S2t2
    40 × 9 = 60 × t2
    t2 =
    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, S1 = 40, t1 = 9
    S2 = 60, t2 = ?
    S1t1 = S2t2
    40 × 9 = 60 × t2
    t2 =
    4 × 9
    = 6 hours.
    6



  1. A car goes 10 metres in a second. Find its speed in km/hour.
    1. 40
    2. 32
    3. 48
    4. 36

  1. 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