Question

Five years ago mean age of a family
was 25 years. What is the present
mean age of the family.​

Answer 1

Let the number of family members be 'x'

The average age of the family members 5 years ago is 25 years

The sum of age of all family members 5 years ago = 25 into x = 25x

the sum of age of these family members now and after 5 years elapsed = 25 x (these added 5 years * no of family members)  = 25x + 5x = 30x

Sum of ages = 30x

No. family members = x

$Current\ average\ age = \frac{Sum\ of\ ages}{No.\ of\ members } = \frac{30x}x} = 30$

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