Question

The average age of a group of 4 friends is 36 years. The youngest friend amongst them is 6 years old. What was the average age of the group at the time of the birth of the youngest friend?​

Answer 1

30 years is the average age of the group

Answer 2

Given :

Average age of a group = 36 years

Number of friends = 4

Age of youngest friend = 6 years

To find : Average age of group when the birth of the youngest friend = ?

Solution :

Sum of ages of a group = $36\times 4=144$

Before 6 years ago,

Sum of ages of a group would be

$144-6\times 4\\\\=144-24\\\\=120$

So, Average age of 3 groups of friends would be

$\dfrac{120}{3}=40$

Hence, the average age of 3 groups of friends is 40 years.