Ve so do:
Do hang don vi gap doi hang tram + hang chuc nen ta co:
Hang don vi: 2 phan.
Hang tram + hang chuc: 1 phan
Ma: hang tram + hang chuc + hang don vi = 9
Nen nhin vao so do ta co: Moi phan bang nhau la: 9: 3 = 3.
Vay hang don vi la: 3 x 2 = 6
Hang tram + hang chuc la: 3
Vay so co 3 chu so la: 306
bai cua cau to đã làm rồi nhung to khong nho tu tu to mới nghĩ ra.