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The average age of a family of 5 members is 20 years, with the youngest member being 5 years old. What was the average age (in years) of the family just before the birth of the youngest member?

The average age of a family of 5 members is 20 years, with the youngest member being 5 years old. What was the average age (in years) of the family just before the birth of the youngest member? Correct Answer 18.75

Given:

Average age of 5 members = 20 years

Age of the youngest member = 5 years

Formula Used:

Average = Sum of age/Number of members

Calculation:

Total age of 5 members = 5 × 20 = 100 years

⇒ Total age of other 4 members = (100 – 5) = 95 years

Total age of other 4 members before 5 years = (95 – 4 × 5) = 75 years

∴ Average age of the family just before the birth of the youngest member = 75/4 = 18.75 years

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