Viết mỗi số tự nhiên dưới dạng một phân số có mẫu bằng \(1\) (theo mẫu) :
Mẫu : \(\displaystyle8 = {8 \over 1}\)
\(\displaystyle5 = \;...\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\;\quad \quad\quad\quad12 =\; ...\)
\(1 = \;...\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\quad\quad\quad\;\;0 =\; ...\)
\(\displaystyle5 = {5 \over 1}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\quad\quad12 = {{12} \over 1}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\quad\quad\)\( \displaystyle 1 = {1 \over 1}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\quad\quad0 = {0 \over 1}\)
-- Mod Toán lớp 4