5Dec19 FS Q41

41Given below is question (Q) followed by three statements. Identify the statements (A. B. C) that are necessary to answer the question.
Question: What is the average age of 300 students studying in a class?
(A) Boys and girls in the class are in the ratio 7:8
(B) The average age of boys and girls is 12.2 years and 11.4 years. respectively.
(C) The number of boys in the class is two less than the number of the girls in the class.
Choose the correct option from those given below:

Option : D
Explanation :
(A) Number of boys and girls are 7x and 8x respectively.
(B) Average age of boys = 12.2 years.
Average age of girls = 11.4 years.
(C) Number of girl- Number of boy = 2
From (A) and (C)
8x - 7x = 2 ⇒ x = 2.
∴ Number of boys = 7x = 14
Number of girls = 8x = 16
From (B), Sum of age of all boys.
= 12.2 x 14 = 170.8
Sum of age of all girls = 16 x 11.4 = 182.4
∴ Average age of 30 students = (170.8 + 182.4)/30 = 11.77 years
Hence, statement either (A) are (C) and (B) are required

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