The average age of group of 5 friends is 32 years. The youngest friend amongst them is 4 years old. What was the average age of the group at the time of birth of the youngest friend?

35 years

Average age of 5 Friends → 32 years

Sum of their ages ⇒ 32 × 5 = 160 years

The youngest one is 4 year old,

4 years ago sum of ages of remaining 4 friends = 160 – (4 × 5) = 160 – 20 = 140 years

Average age of group at the time of birth of youngest one is $\frac{140}{4} = 35$ years