#66 Average Quantitative Aptitude Question

8 years ago there were 5 members in the Arthur's family and then the average age of the family  was 36 years. Mean while Arthur got married and gave birth to a child. Still the average age of his family is same now. What is the age of his wife at the time of his child's birth was.If the difference between the age of her  child and herself was 26 years.

A) 25 years
B) 26 years
C) 20 years
D) can't be determined

 Answer: B) 26 years 

Explanation:

Since we know that the difference b/w the age of any two persons remains always constant, while the ratio of their ages gets changed as the time changes.

so, if the age of his child be x (presently)

Then the age of  wife be x + 26 (presently)

Thus the total age = x + ( x + 26) = 32  [ 252-220 =32]

 x = 3

 The age of her child is 3 years and her self  is 29 years. Hence her age at the time of the birth of her child was 26 years.