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Aptitude miscellaneous
  1. A boy found that the average of 20 numbers is 35 when he writes a number ‘61’ instead of ‘16’. The correct average of 20 numbers is








  1. View Hint View Answer Discuss in Forum

    Given that , The average of 20 numbers = 35
    When a boy writes a number ‘61’ instead of ‘16’ , then

    Correct average = 35 +
    61 -16
    20

    Correct average = 35 -
    45
    		 = 35 - 2.25 = 32.75
    20

    Second method to solve this question with the help of given formula :
    Here, n = 20, m = 35 , a = 16, b = 61

    Correct Option: A

    Given that , The average of 20 numbers = 35
    When a boy writes a number ‘61’ instead of ‘16’ , then

    Correct average = 35 +
    61 -16
    20

    Correct average = 35 -
    45
    		 = 35 - 2.25 = 32.75
    20

    Second method to solve this question with the help of given formula :
    Here, n = 20, m = 35 , a = 16, b = 61
    Correct mean = m +
    (a - b)
    n

    Correct mean = 35 +
    (16 - 61)
    20

    Correct mean = 35 -
    45
    20

    Correct mean = 35 – 2.25 = 32.75

  1. The average weight of 12 crewmen in a boat is increased by 1/3 kg, when one of the crewmen whose weight is 55 kg is replaced by a new man. What is the weight of that new man?








  1. View Hint View Answer Discuss in Forum

    Total increase in weight = 12 ×
    1
    		 = 4
    3

    Weight of the new man = Weight of the crewmen + Total increase in weight
    ∴ Weight of the new man = 55 + 4 = 59 kg
    Second method to solve this question with the help of given formula :
    Here, N = 12, T = 55, t =
    1
    3

    Weight of new man = T + Nt

    Correct Option: D

    Total increase in weight = 12 ×
    1
    		 = 4
    3

    Weight of the new man = Weight of the crewmen + Total increase in weight
    ∴ Weight of the new man = 55 + 4 = 59 kg
    Second method to solve this question with the help of given formula :
    Here, N = 12, T = 55, t =
    1
    3

    Weight of new man = T + Nt
    Weight of the new man = 55 + 12 ×
    1
    3

    Weight of the new man = 55 + 4 = 59 kg.

  1. Average weight of 25 persons is increased by 1 kg when one man weighing 60 kg is replaced by a new person. Weight of new person is :








  1. View Hint View Answer Discuss in Forum

    According to question ,
    Total weight increased = 1 × 25 = 25 kg
    ∴ Weight of new person = weight of man + Total weight increased
    Weight of new person = 60 + 25 = 85 kg
    Second method to solve this question with the help of given formula :
    Here, N = 25, T = 60 , t = 1

    Correct Option: D

    According to question ,
    Total weight increased = 1 × 25 = 25 kg
    ∴ Weight of new person = weight of man + Total weight increased
    Weight of new person = 60 + 25 = 85 kg
    Second method to solve this question with the help of given formula :
    Here, N = 25, T = 60 , t = 1
    Weight of New person = T + Nt
    Weight of New person = 60 + 25 × 1 = 85 Kg

  1. The average weight of 20 students in a class is increased by 0.75 kg when one of the students weighing 30 kg is replaced by a new student. Weight of the new student (in kg) is :








  1. View Hint View Answer Discuss in Forum

    Here , Increase in weight = 0.75 kg
    According to question ,
    Required answer = 30 + 20 × 0.75
    Required answer = 30 kg + 15 kg = 45 kg
    Second method to solve this question with the help of given formula :
    Here, N = 20, T= 30, t = 0.75
    Weight of New student = T + Nt

    Correct Option: C

    Here , Increase in weight = 0.75 kg
    According to question ,
    Required answer = 30 + 20 × 0.75
    Required answer = 30 kg + 15 kg = 45 kg
    Second method to solve this question with the help of given formula :
    Here, N = 20, T= 30, t = 0.75
    Weight of New student = T + Nt
    Weight of New student = 30 + 20 × 0.75
    Weight of New student = 30 + 15 = 45 kg

  1. The average of 9 integers is found to be 11. But after the calculation, it was detected that, by mistake, the integer 23 was copied as 32, while calculating the average. After the due correction is made, the new average will be








  1. View Hint View Answer Discuss in Forum

    Here , The average of 9 integers = 11
    ⇒ Sum of 9 integers = 9 × 11 = 99.

    New average =
    99 + 23 - 32
    		 =
    90
    99

    New average = 10
    Second method to solve this question with the help of given formula :
    Here, n = 9, m = 11 , a = 23, b = 32
    Correct mean = m +
    (a - b)
    n

    Correct Option: A

    Here , The average of 9 integers = 11
    ⇒ Sum of 9 integers = 9 × 11 = 99.

    New average =
    99 + 23 - 32
    		 =
    90
    99

    New average = 10
    Second method to solve this question with the help of given formula :
    Here, n = 9, m = 11 , a = 23, b = 32
    Correct mean = m +
    (a - b)
    n

    Correct mean = 11 +
    (23 - 32)
    9

    Correct mean = 11 +
    ( - 9)
    9

    Correct mean = 11 – 1 = 10