B1: Voi cung ca 4 chu so :9;6;3;2 co the viet tat ca bao nhieu chu so co 4 chu so
B2: Ban Gia mua 1 quyen sach day 678 trang.Ban Gia danh so trang tu 1 den 678.Hoi can viet bao nhieu chu cac chu so de danh het so trong quyen sach
B3:khi viet tat ca cac so tu nhien tu 1den 100 thi
A,chu so 2 lap lai bao nhieu lan
B,chu so 3 lap lai bao nhieu lan
cac ban lam tung bai mot cung dc
cam on cac ban
