What is the average age for a thirteen year old girl?

Answer 1

A thirteen year old is 13 years old.

Unless they are from China (or Another Country which uses adjusted age).

In the United States (and more than likely most of Europe, Canada, etc) age is typically counted on the first birthday with the birth age starting at 0, so when you have lived for 12 months your age becomes 1.

However in some cultures (notably China), age is counted as "the number of years inside of which you have lived".

What this means is a newborn baby on his first day is "within his first year" and is called a 1 year old. By the time it reaches its first birthday after 12 months it is now "entering its second year" and is now a 2 year old.

So a 13 year old in China is only 12 years old by most other cultures counting standards. Because a 12 year old is "living within his 13th year" and by Chinese standards would be called 13 years old when in reality they are 12 years (and however many months).

Answer 2

Averaged, it is thirteen years!