Averages questions and answers : Quantitative Aptitude

  • What is the average of first 21 multiples of 7 ?

    A.) 49 B.) 77
    C.) 66 D.) 57
    Answer: Option 'B'

    Required average  = 7(1+2+....+21) / 21

    (7/21)X ( (21x22) / 2 )  (because sum of first 21 natural numbers)

    = 77



  • In a class, the average age of 30 boys is 13 years and the average of 20 girls is 12 years. what is the average age of the whole class?

    A.) 12.5 Yrs B.) 14.2 Yrs
    C.) 12.3 Yrs D.) 12.6 Yrs
    Answer: Option 'D'

    Total age of 50 students

    (30X 13+20 X 12) = 630

    Average =  630/50 = 12.6 Years



  • The average age of a class of 32 students is 16 yrs. if the teacher's age is also included, the average increases by one year. Find the age of the teacher

    A.) 49 B.) 48
    C.) 47 D.) 50
    Answer: Option 'A'

    Total age of students is 32X16 = 512 Years

    Total age inclusive of teacher = 33X (16+1) = 561

    So, Teacher's age is 561-512 = 49 Yrs

    There is a shortcut for these type of problems

    Teacher's age is 16+(33X1) = 49 Years



  • The average of seven numbers is 18. The average of first three numbers is 14 and the average of last three numbers is 19. What is the middle number?

    A.) 42 B.) 57
    C.) 27 D.) None of these
    Answer: Option 'C'

    The total of seven numbers = 7X18 = 126

    The total of first 3 and last 3 numbers is = 3 X 14+3 X 19 = 99

    So, the middle number is (126 - 99 ) = 27



  • Average of five consecutive even numbers is 35. Find the greatest number in these five numbers?

    A.) 31 B.) 33
    C.) 39 D.) 36
    Answer: Option 'C'



  • Average of 13 results is 65. If the average of first six results is 61 and average of last six results is 59 Then find the seventh result?

    A.) 115 B.) 135
    C.) 125 D.) 105
    Answer: Option 'C'



  • The average weight of a class of 20 boys was calculated to be 58.4 kgs and it was later found that one weight was misread as 56 kg instead of 65 kg. What is the correct weight?

    A.) 67.4kg B.) 57.75kg
    C.) 58.85kg D.) 49.4kg
    Answer: Option 'C'

    Actual total weight is (20X 58.4 - 56 + 65) = 1177 Kgs

    Actual average weight is 1177/20 = 58.85kgs





Quantitative Aptitude Topics


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