Question

The average age of a family of five members is 24 years. If the present age of the youngest member is 88 years, what was the average age of the family at the time of the birth of the youngest member?
a) 50
b) 40
c) 30
d) 20

Answer 1

Let the Total Present age of everymember in the family be =x years.
Given: there are 5 members in total.

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So x/5=24 { From the question} →(1)

at the time of birth The youngest would be 0 years. and Each Members present age will Be differenced by 88.

So 88× 5 must be Cut of from x .

i.e. Avg. age. 88years ago=(x-(88×5)/5→(2)

Now from (1)
x=24×5
Substituting this in (2)

→[(24×5)-(88×5)/5]=5(24-88)/5=(-64)years...

Since age cant be negative...

So the avg age would be 64 years...
}}}}

Then Again. Look Lets take the Youngest age to be 8years.

So at the time of the youngests birth...

Avg age=[(24×5)-(4×5)]/5
=24-4=20...

so If the Present age of the youngest is 8 years..

Then Avg. age 8 years ago is 20 years.

So the Answer is (d)

Hope it helps...
Regards,
Leukonov.