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Aptitude miscellaneous
  1. The average of 25 results is 18; that of first twelve is 14 and of last twelve is 17. Find the thirteenth result.








  1. View Hint View Answer Discuss in Forum

    The average of 25 results =18;
    Sum of 25 results = Average × their number
    Sum of 25 results = 18 × 25 = 450
    The average of first twelve = 14
    Similarly, Sum of 1st twelve results = 12 × 14 = 168
    and The average of last twelve = 17

    Correct Option: B

    The average of 25 results =18;
    Sum of 25 results = Average × their number
    Sum of 25 results = 18 × 25 = 450
    The average of first twelve = 14
    Similarly, Sum of 1st twelve results = 12 × 14 = 168
    and The average of last twelve = 17
    and sum of last twelve results = 12 × 17 = 204
    ∴ Thirteenth result = 450 – 168 – 204 = 78

  1. The average height of 30 girls out of a class of 40 is 160 cms and that of the remaining girls is 156 cms. What is the average height of the whole class?








  1. View Hint View Answer Discuss in Forum

    As per the given in question ,
    Total height of the whole class = (30 × 160) + (40 – 30) × 156 = 6360 cms

    Correct Option: C

    As per the given in question ,
    Total height of the whole class = (30 × 160) + (40 – 30) × 156 = 6360 cms
    Average height of the whole class = 6360 ÷ 40 = 159 cms.

  1. a, b, c, d and e are five consecutive odd numbers. What is their average?








  1. View Hint View Answer Discuss in Forum

    According to question ,
    Each successive odd number exceeds its predecessor by 2.
    a + b + c + d + e = a + (a + 2) + (a + 4) + (a + 6) + (a + 8) = 5a + 20 = 5 (a + 4)

    Average age =
    5(a + 4)
    5

    Correct Option: B

    According to question ,
    Each successive odd number exceeds its predecessor by 2.
    a + b + c + d + e = a + (a + 2) + (a + 4) + (a + 6) + (a + 8) = 5a + 20 = 5 (a + 4)

    Average age =
    5(a + 4)
    		 = a + 4
    5

  1. The average age of three boys is 15 years. If their ages are in the ratio 3 : 5 : 7, what is the age of the youngest boy?








  1. View Hint View Answer Discuss in Forum

    Let the age of three boys be 3k, 5k and 7k
    According to question ,

    Average age =
    3k + 5k + 7k
    		 = 5k
    3

    Correct Option: A

    Let the age of three boys be 3k, 5k and 7k
    According to question ,

    Average age =
    3k + 5k + 7k
    		 = 5k
    3

    and, 5k = 15 ⇒ k = 3 years
    The age of the youngest boy = 3k = 9 years.

  1. Out of three numbers, the first is twice of the second and is half of the third. If the average of three numbers is 56, find the largest number.








  1. View Hint View Answer Discuss in Forum

    Let the first number be y.
    Second number = y / 2
    Third number = 2y

    Average =
    y + (y/2) + 2y
    		=
    7
    		y
    36

    Correct Option: C

    Let the first number be y.
    Second number = y / 2
    Third number = 2y

    Average =
    y + (y/2) + 2y
    		=
    7
    		y
    36

    Given :
    7
    		y = 56 ⇒ y = 48
    6

    So, the three numbers are 48, 24 and 96.