The average age of four brothers is 12 years. If the age of their mother is also included, the average is increased by 5 years. The age of the mother (in years) is :
Options:
A . 43 years
B . 37 years
C . 53 years
D . 48 years
Answer: Option B Answer: (b)Average age of 4 brothers = 12 yrs. Total age of 4 brothers = 4 × 12 = 48 yrs. Average age of 4 brothers + mother ( = 5 persons) = 12 + 5 = 17 yrs. ∴Total age of 4 brothers + mother = 5 × 17 = 85 yrs. ∴The age of the mother = 85 – 48 = 37 yrs. Aliter : Using Rule 24, ( If a new member is added in a group then. age (or income) of added member = Average (or income) ± x (n + 1) where x = increase (+) or decrease (–) in average age (or income) n = Number of members. )Here, x = 5, n = 4 Age of mother = Average+x (n+1) = 12 + 5 (4 + 1) = 12 + 25 = 37 years
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