Question

Average age of a family of 5 members is 20 years.With a youngest member being 5 years old .What is the average age of family just before tge birth of youngest member

Answer 1

Given,

The average age of family= 20

Number of members in the family = 5

Average = Sum of Observations/ Number of observations

let the number of observations be x

20 = x/5

20 × 5 = x

x = 100

Thus, the total ages of family of 5 members is 100.

If one member of 5 years is excluded then the average = ?

Subtract the age of youngest member from the total ages.

100 - 25 = 75 years.

Now sum of ages of 4 members is 75 years.

Average of 4 members = 75/4 = 18.75

Therefore, the average of family was 18.75

Answer 2

Let sum of age of all 5 members of a family is = X

Average = X/5 = 20. ( given)

sum of age of 5 members (X) = 100

Age of younger member = 5 years. ( given)

Sum of age with out younger member =

X/4 = 20

X = 80-5

X = 75

So

Average age with out younger member = 75/4 = 18.75 years.