Speed, Time and Distance


  1. A man completes 30 km of a journey at the speed of 6 km/hr and the remaining 40 km of the journey in 5 hours. His average speed for the whole journey is
    1. 7 km/hr
    2. 6
      4
      km/hr
      11
    3. 8 km/hr
    4. 7.5 km/hr

  1. View Hint View Answer Discuss in Forum

    Time taken to cover 30km at 6 kmph =
    30
    = 5 hours
    6

    Time taken to cover 40 km = 5 hours
    ∴  Average speed =
    Total distance
    Time taken

    =
    30 + 40
    10

    =
    70
    = 7 kmph
    10

    Correct Option: A

    Time taken to cover 30km at 6 kmph =
    30
    = 5 hours
    6

    Time taken to cover 40 km = 5 hours
    ∴  Average speed =
    Total distance
    Time taken

    =
    30 + 40
    10

    =
    70
    = 7 kmph
    10


  1. One third of a certain journey is covered at the rate of 25 km/hour, one-fourth at the rate of 30 km/hour and the rest at 50 km/hour. The average speed for the whole journey is
    1. 35 km/hour
    2. 33
      1
      km/hr
      3
    3. 30 km/hour
    4. 37
      1
      km/hr
      12

  1. View Hint View Answer Discuss in Forum

    Let the total distance be x km.

    Total time =
    x
    x
    5x
    3
    +
    4
    +
    12
    253050

    =
    x
    +
    x
    +
    x
    75120120

    =
    x
    +
    x
    7560

    =
    4x + 5x
    =
    3x
    hours
    300100

    ∴  Average speed =
    Total distance
    Time taken


    =
    x
    3x
    100

    =
    100
    = 33
    1
    kmph
    33


    Second Method :
    Here, x = 3, u = 25, y = 4, v = 30
    z =
    12
    , w = 50
    5

    Average Speed =
    1
    1
    +
    1
    +
    1
    xuyvzw

    =
    1
    1
    +
    1
    +
    1
    3 × 254 × 30(12/5) × 50

    =
    1
    1
    +
    1
    +
    1
    75120120

    =
    1
    1
    +
    1
    7560


    =
    1
    4 + 5
    300

    =
    300
    =
    100
    93

    = 33
    1
    km/hr.
    3

    Correct Option: B

    Let the total distance be x km.

    Total time =
    x
    x
    5x
    3
    +
    4
    +
    12
    253050

    =
    x
    +
    x
    +
    x
    75120120

    =
    x
    +
    x
    7560

    =
    4x + 5x
    =
    3x
    hours
    300100

    ∴  Average speed =
    Total distance
    Time taken


    =
    x
    3x
    100

    =
    100
    = 33
    1
    kmph
    33


    Second Method :
    Here, x = 3, u = 25, y = 4, v = 30
    z =
    12
    , w = 50
    5

    Average Speed =
    1
    1
    +
    1
    +
    1
    xuyvzw

    =
    1
    1
    +
    1
    +
    1
    3 × 254 × 30(12/5) × 50

    =
    1
    1
    +
    1
    +
    1
    75120120

    =
    1
    1
    +
    1
    7560


    =
    1
    4 + 5
    300

    =
    300
    =
    100
    93

    = 33
    1
    km/hr.
    3



  1. A man goes from a place A to B at a speed of 12 km/hr and returns from B to A at a speed of 18 km/hr. The average speed for the whole journey is
    1. 14
      2
      km/hr
      5
    2. 15 km/hr
    3. 15
      1
      km/hr
      2
    4. 16 km/hr

  1. View Hint View Answer Discuss in Forum

    Average speed =
    2xy
    kmph
    x + y

    =
    2 × 12 × 18
    kmph
    12 + 18

    =
    2 × 12 × 18
    kmph
    30

    = 14
    2
    kmph
    5

    Correct Option: B

    Average speed =
    2xy
    kmph
    x + y

    =
    2 × 12 × 18
    kmph
    12 + 18

    =
    2 × 12 × 18
    kmph
    30

    = 14
    2
    kmph
    5


  1. A man goes from Mysore to Bangalore at a uniform speed of 40 km/hr and comes back to
    Mysore at a uniform speed of 60 km/hr. His average speed for the whole journey is
    1. 48 km/hr
    2. 50 km/hr
    3. 54 km/hr
    4. 55 km/hr

  1. View Hint View Answer Discuss in Forum

    Average speed =
    2xy
    kmph
    x + y

    =
    2 × 40 × 60
    kmph
    40 + 60

    = 48 kmph

    Correct Option: A

    Average speed =
    2xy
    kmph
    x + y

    =
    2 × 40 × 60
    kmph
    40 + 60

    = 48 kmph



  1. A person went from A to B at an average speed of x km/hr and returned from B to A at an average speed of y km/hr. What was his average speed during the total journey ?
    1. x + y
      2xy
    2. 2xy
      x + y
    3. 2
      x + y
    4. 1
      +
      1
      xy

  1. View Hint View Answer Discuss in Forum

    Required average speed =
    2xy
    kmph
    x + y

    [Since, can be given as corollary If the distance between A and B be z units, then
    Average speed =
    Total distance
    Time taken

    =
    z + z
    z
    +
    z
    xy

    =
    2
    1
    +
    1
    xy

    =
    2
    x + y
    xy

    =
    2xy
    x + y

    Correct Option: B

    Required average speed =
    2xy
    kmph
    x + y

    [Since, can be given as corollary If the distance between A and B be z units, then
    Average speed =
    Total distance
    Time taken

    =
    z + z
    z
    +
    z
    xy

    =
    2
    1
    +
    1
    xy

    =
    2
    x + y
    xy

    =
    2xy
    x + y