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Aptitude miscellaneous
  1. The average weight of 15 oarsmen in a boat is increased by 1.6 kg when one of the crew, who weighs 42 kg is replaced by a new man. Find the weight of the new man (in kg).








  1. View Hint View Answer Discuss in Forum

    Here, N = 15, T = 42, t = 1.6
    We can find required answer with the help of given formula ,
    Weight of new oarsman = ( N + T × t )
    Weight of new oarsman = (42 + 15 × 1.6) kg.

    Correct Option: C

    Here, N = 15, T = 42, t = 1.6
    We can find required answer with the help of given formula ,
    Weight of new oarsman = ( N + T × t )
    Weight of new oarsman = (42 + 15 × 1.6) kg.
    ∴ Weight of new oarsman = (42 + 24) kg. = 66 kg.

  1. The average marks of a class of 35 children is 35. The marks of one of the students, who got 35, was incorrectly entered as 65. What is the correct average of the class?








  1. View Hint View Answer Discuss in Forum

    According to question ,
    Total correct marks of 35 children = 35 × 35 + 35 – 65 = 1225 – 30 = 1195

    Required average =
    1195
    		 = 34.14
    35

    Second method to find the required average ,
    Diffference = – 65 + 35 = – 30

    Correct Option: B

    According to question ,
    Total correct marks of 35 children = 35 × 35 + 35 – 65 = 1225 – 30 = 1195

    Required average =
    1195
    		 = 34.14
    35

    Second method to find the required average ,
    Diffference = – 65 + 35 = – 30
    Required average = 35 –
    30
    35

    Required average = 35 – 0.857 = 34.143

  1. The average of 20 numbers is calculated as 35. It is discovered later on that while calculating the average, one number, namely 85, was mis read as 45. The correct average is :








  1. View Hint View Answer Discuss in Forum

    Here , The average of 20 numbers = 35
    Sum of 20 numbers = 20 × 35
    According to question ,
    Correct sum of 20 numbers = 20 × 35 – 45 + 85
    Correct sum of 20 numbers = 700 + 40 = 740

    Correct Option: C

    Here , The average of 20 numbers = 35
    Sum of 20 numbers = 20 × 35
    According to question ,
    Correct sum of 20 numbers = 20 × 35 – 45 + 85
    Correct sum of 20 numbers = 700 + 40 = 740

    ∴ Required average =
    740
    		 = 37
    20

  1. If the arithmetic mean of 7, 5, 13, x and 9 is 10, then the value of x is :








  1. View Hint View Answer Discuss in Forum

    According to the question,

    Average =
    Sum of given numbers
    Total numbers of terms

    ⇒ 10 =
    7 + 5 + 13 + x + 9
    5

    ⇒ 7 + 5 + 13 + x + 9 = 10 × 5

    Correct Option: D

    According to the question,

    Average =
    Sum of given numbers
    Total numbers of terms

    ⇒ 10 =
    7 + 5 + 13 + x + 9
    5

    ⇒ 7 + 5 + 13 + x + 9 = 10 × 5
    ⇒ 34 + x = 50
    ⇒ x = 50 – 34 = 16

  1. The average of 20 numbers is 12. The average of the first 12 numbers is 11 and that of the next 7 numbers is 10. The last number is :








  1. View Hint View Answer Discuss in Forum

    Here , Sum of 20 numbers = 20 × 12
    sum of first 12 numbers = 11 × 12
    sum of next 7 numbers = 7 × 10
    ∴ Last number = Sum of 20 numbers – sum of first 12 numbers – sum of next 7 numbers

    Correct Option: B

    Here , Sum of 20 numbers = 20 × 12
    sum of first 12 numbers = 11 × 12
    sum of next 7 numbers = 7 × 10
    ∴ Last number = Sum of 20 numbers – sum of first 12 numbers – sum of next 7 numbers
    Last number = 20 × 12 – 11 × 12 – 7 × 10
    Last number = 240 – 132 – 70 = 38