Question

three years ago the average age of a family of 5 members was 17 years. in spite of the birth of a child in the family the present average of the family remains the same. the present age of a child is

Answer 1

Average = (Total quantity)/(No. of quantities)

So,

Let the present age of the child be x

Now, three years back, the average age of family was 17

So,

Total age = 17×5 = 85 years

Now,

The present age average is still 17

So, in three years the individual age of the members will also increase

Increase in age of five family members = 5×3 = 15

So,

By present,

(15+85+x)/6 = 17

x=102 - 100

x=2

So,

The present age of the child is 2 years

Answer 2

Find the sum of the age of the family of 5, 3 years ago:

Average = 17

Sum = 17 x 5 = 85 years

Find the sum of the age of the family of 5, now:

There are 5 members. Each member will have increased by 3 years.

Total increase = 5 x 3 = 15

Sum of their age now = 85 + 15 = 100 years

Find the sum of the age of the family of 6 (including the new addition):

Average = 17 (It is said that there is no increase in the average)

Sum = 17 x 6 = 102

Find the age of the new addition:

Child's age = 102 - 100 = 2 years old

Answer: The child is 2 years old