Ask two math questions (written in Wenzhou, Zhejiang Province in 2009)
Solution: As shown in the figure, intersection A is AD⊥BC of point D and EF of point G.
Δ δAEF?δABC of EF//BC
EF/BC=AG/AD
EF=3，BC= 15，AD=22.5
3/ 15=AG/22.5，
AG=4.5
GD=AD-AG=22.5-4.5= 18
18÷3=6
A:
This square piece of paper is the sixth.