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The average age of a family of 6 members is 25 years. If the youngest member of the family is of 12 years age, then what was the average age of the family just at the moment of the birth of the youngest member?

The average age of a family of 6 members is 25 years. If the youngest member of the family is of 12 years age, then what was the average age of the family just at the moment of the birth of the youngest member? Correct Answer 13

The present average age of family = 25

⇒ Average = total age/number of family members

⇒ Thus, present total age of the family = average × no. of members = 25 × 6 = 150

Now,

Youngest member is 12 years old, thus,

Before 12 years that is at the time of birth of youngest child

⇒ Total age of the family would be = 150 – (12 × 6)  

(∵ before 12 years, members were 12 years younger than their present age)

⇒ Total age before 12 years = 78

∴ Average = 78/6 = 13

If there is a new born member in the family and the average age is calculated for that family at the time of birth or after the birth then the baby is considered as a member in calculation. 

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