Answer:
5 pieces
Explanation:
original pieces of paper = 11
some cut into = 3 parts
new pieces of paper = 21
21 / 3 = 7 pieces were cut into three parts to make 21 pieces of paper,
but according to the question some of the paper got cut into three parts,
so we will stick to 5 pieces that were cut into three parts
as,
5*3 = 15 pieces
pieces left = 6
total = 21 pieces
thus, 5 pieces were cut into three equal parts