Question

The mean age at the beginning of the growth spurt in girls is _____, peaking at age _____.

Answer 1

In most girls, the beginning of their pubescent years starts around the age of 9, and ends around 11 1/2.

NOTE: This is the mean. It is not an absolute when a human will start puberty. Everyones body is different in this regard.

So to answer your question:
The mean age at the beginning of the growth spirt in girls is 9, peaking at age 11.5.

Hope this helps! If you have any questions, please just ask!
Chandowd