The average age of a family of 5 members is 20 years. If the age of th

Question

The average age of a family of 5 members is 20 years. If the age of the youngest member be 10 years then what was the average age of the family at the time of the birth of the youngest member?

A. 9.5 
B. 10.5
C. 11.5 
D. 12.5
E. 13.5

Tumilara · Accepted Answer

This is a poor question in my opinion. At the time the youngest child is born, his/her age is 0. so it should be 50/5=10

Archit3110 · Answer

so total age of family = 5*20 ; 100
now age of youngest member = 10 
and at time of birth of youngest member all members age will be reduced by 10 each or say 10*5 ; 50 
so 100-50 = 50 
avg of family then ; 50/4 ; 12.5 IMO D

Abhishek009 · Answer

\frac{5*20 - 4*10 - 10 }{4 }=12.50  Answer must be (D)

Gauravji21 · Answer

I agree too.

For me, at the time of birth means the baby is born and if baby is born then there will be 05 family members.
I initially calculated for 05 members and got 10 years as the average age. 
Since, 10 was not thr in the answer choice, i took the number of family members as 4. Got the answer as 12.5.

But yes, had difficulty in understanding the exact meaning of the question. It was the answer choices which helped in deciding the # of family members.

ScottTargetTestPrep · Answer

Solution:

The sum of the ages of the 5 members of the family is 20 x 5 = 100 years. Excluding the youngest member who is 10 years old, the sum of the ages of the 4 remaining members is 90 years. Therefore, their average age is 90/4 = 22.5 years. However, at the time of the birth of the youngest member, i.e., 10 years ago, their average age was 10 years less, or 12.5 years.

Answer: D

AnirudhaS · Answer

(100-50)/4 = 12.5 years

Answer:  D

GmatPoint · Answer

Total age of the family = 20*5 = 100
Since we have to find the average of the family when the youngest member was born, the total age of the family when the youngest member was born = 100 - 10*5 = 50.

Since now, the member are 4,
Average age = 50/4 = 12.5

Thus, the correct answer is D(Though the right answer should be 10).

boosnackman · Answer

There would be 5 family members "at the time of the birth of the youngest member".

aryanrgupta · Answer

This question has no correct option.  The answer should be 10 . Since the average age is 20 currently, the age 10 years would (Age - 10) for all the members.

So..... Family Member (FM)

FM1-10, FM2-10, FM3-10, FM4-10, FM5-10 ...... as all elements shed 10 the average would also shed 10 (by property of averages)

ANSWER:  (20-10)=10.

The average age of a family of 5 members is 20 years. If the age of th

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The average age of a family of 5 members is 20 years. If the age of th

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