Question

where in the book the boy in the striped pajamas does it say gretels age

Answer 1

I don't know exactly where. Bruno is nine years old, and Gretel is three years older than him, making her twelve. Like I said, I don't know where it says that though... I'd check near the beginning of the book, where Bruno calls Gretel a "hopeless case".

Answer 2

Answer: She's 12-13

Explanation: I don't know the exact chapter but she was 12 at the start of the book and at the end she was 13.