Marguerite, Maya's character in the book, says she was around ten years old at the time the incident occurred.
In Chapter 5, Marguerite describes the incident when the "powhitetrash" girls caused "the most painful and confusing experience (she) had ever had with (her) grandmother". The ill-behaved children came into her grandmother's store and one of the girls audaciously did a handstand, brazenly showing that she wore no underwear while her friends egged her on. Because of the social climate of the times, Marguerite's grandmother could not reprimand the children but had to bear the affront without protest, and address the children by name with the respectful title "Miz" as they left the store. Marguerite is infuriated, and although she does not understand how her grandmother can endure it, she does recognize that by responding with untouchable dignity, her grandmother somehow had "won" the confrontation that had occurred.
In Chapter Five, Marguerite says she was about ten years old when the incident occured.