Unitary Method


  1. 10 men, working 6 hours a day can complete a work in 18 days. How many hours a day must 15 men work to complete the work in 12 days?









  1. View Hint View Answer Discuss in Forum

    According to given question,
    10 men, can complete a work in 18 days by working 6 hours a day.
    1 men, can complete a work in 18 days by working 6 x 10 hours a day.
    1 men, can complete a work in 1 days by working 6 x 10 x 18 hours a day.

    15 men, can complete a work in 1 days by working
    6 x 10 x 18 hours a day.
    15

    15 men, can complete a work in 12 days by working
    6 x 10 x 18 hours a day.
    15 x 12

    Correct Option: C

    According to given question,
    10 men, can complete a work in 18 days by working 6 hours a day.
    1 men, can complete a work in 18 days by working 6 x 10 hours a day.
    1 men, can complete a work in 1 days by working 6 x 10 x 18 hours a day.

    15 men, can complete a work in 1 days by working
    6 x 10 x 18 hours a day.
    15

    15 men, can complete a work in 12 days by working
    6 x 10 x 18 hours a day.
    15 x 12

    15 men, can complete a work in 12 days by working
    1 x 10 x 6 hours a day.
    5 x 2

    15 men, can complete a work in 12 days by working
    6 hours a day.
    1

    15 men, can complete a work in 12 days by working 6 hours a day.


  1. Nine engines consume 24 metric tonnes of coal, when each is working 8 hours day. How much coal is required for 8 engines, each running 13 hours a day, if 3 engines of former type consume as much as 4 engines of latter type?









  1. View Hint View Answer Discuss in Forum

    Let required amount of coal be y metric tonnes .
    9 engines consumes 24 metric tonnes of coal in 8 hours a day.
    More engines, more amount of coal (direct proportion)
    If 3 engines of first type consume 1 unit, then 1 engine will consume 1/3 unit which is its the rate of consumption.
    If 4 engines of second type consume 1 unit, then 1 engine will consume 1/4 unit which is its the rate of consumption
    More rate of consumption, more amount of coal (direct proportion)
    More hours, more amount of coal(direct proportion)

    Correct Option: D

    Let required amount of coal be y metric tonnes
    9 engines consumes 24 metric tonnes of coal in 8 hours a day.
    More engines, more amount of coal (direct proportion)
    If 3 engines of first type consume 1 unit, then 1 engine will consume 1/3 unit which is its the rate of consumption.
    If 4 engines of second type consume 1 unit, then 1 engine will consume 1/4 unit which is its the rate of consumption
    More rate of consumption, more amount of coal (direct proportion)
    More hours, more amount of coal(direct proportion)
    Now we have , 9 × ( 1 / 3 ) × 8 × y = 8 × ( 1 / 4 ) × 13 × 24
    ⇒ 3 × 8 × y = 8 × 6 × 13
    ⇒ 3 × y = 6 × 13 ⇒ y = 2 x 13 = 26 metric tonnes



  1. A fort had provision of food for 150 men for 45 days. After 10 days, 25 men left the fort. The number of days for which the remaining food will last, is:









  1. View Hint View Answer Discuss in Forum

    As per the given question ,
    Food of 150 men for 45 days = 150 × 45 = 6750 unit
    After 10 days , Food of 150 men for 150 × 10 = 1500 unit
    And after 10 days remaining men = 150 - 25 = 125
    and remaining food = 6750 - 1500 = 5250 unit
    Let D be the number of days for which the remaining food .

    Correct Option: C

    As per the given question ,
    Food of 150 men for 45 days = 150 × 45 = 6750 unit
    After 10 days , Food of 150 men for 150 × 10 = 1500 unit
    And after 10 days remaining men = 150 - 25 = 125
    and remaining food = 6750 - 1500 = 5250 unit
    Let D be the number of days for which the remaining food .
    So, 125 × D = 5250
    ⇒ D = 5250 /125 = 42 days


  1. Nine examiners can examine a certain number of answer books in 12 days by working 5 hours a day. How many hours in a day should 4 examiners work to examine twice the number of answer books in 30 days?









  1. View Hint View Answer Discuss in Forum

    Here , M1 = 9
    D1 = 12
    H1 = 5
    W1 = 1
    And M2 = 4
    D2 = 30
    H2 = x
    W2 = 2
    We know that ,

    M1 x D1 x H1
    =
    M2 x D2 x H2
    W1W2

    9 x 12 x 5
    =
    4 x 30 x H2
    12





    Correct Option: A

    Here , M1 = 9
    D1 = 12
    H1 = 5
    W1 = 1
    And M2 = 4
    D2 = 30
    H2 = x
    W2 = 2
    We know that ,

    M1 x D1 x H1
    =
    M2 x D2 x H2
    W1W2

    9 x 12 x 5
    =
    4 x 30 x H2
    12

    ⇒ H2 = 9 hours
    Hence required answer = 9 hours .





  1. ‘P’ men working ‘P’ hours per day can do ‘P’ units of a work in ‘P' days. How much work can be completed by ‘Q’ men working ‘Q’ hours per day in ‘Q’ days?









  1. View Hint View Answer Discuss in Forum

    As we know from the given question,
    P men working P hours per day in P days can do P units of a work.
    1 men working P hours per day in P days can do P / P units of a work.
    1 men working 1 hours per day in P days can do P /P x P units of a work.
    1 men working 1 hours per day in 1 days can do P /P x P x P units of a work.
    Q men working 1 hours per day in 1 days can do P x Q /P x P x P units of a work.
    Q men working Q hours per day in 1 days can do P x Q x Q /P x P x P units of a work.

    Correct Option: B

    As we know from the given question,
    P men working P hours per day in P days can do P units of a work.
    1 men working P hours per day in P days can do P / P units of a work.
    1 men working 1 hours per day in P days can do P /P x P units of a work.
    1 men working 1 hours per day in 1 days can do P /P x P x P units of a work.
    Q men working 1 hours per day in 1 days can do P x Q /P x P x P units of a work.
    Q men working Q hours per day in 1 days can do P x Q x Q /P x P x P units of a work.
    Q men working Q hours per day in Q days can do P x Q x Q x Q/P x P x P units of a work.
    Q men working Q hours per day in Q days can do Q3/P2 units of a work.