1. Tim trung binh cong cua tat ca cac so tu nhien co 4 chu so khac nhau duoc viet boi bon chu so 0;3;5;7.Trung binh cong cua tat ca cac so do la?

2 .Tong cua 3 so bang 5,2. So thu nhat bang 2/3 so thu ba va so thu hai bang 50% so thu ba. Tim so thu hai?

3. Tim mot phan so co mau so bang 25 , biet rang neu cong tu so voi 34 va nhan mau so voi 3 thi duoc phan so moi bang phan so da cho. Tim phan so do?

4. Tim mot phan so biet rang neu cong them 4 vao tu so va giu nguyen mau so thi ta duoc phan so moi bang 1, con neu giu nguyen tu so va cong them 3 thi ta duoc phan so moi bang 1/2 .Tim phan so do?

5. Hay cho biet co tat ca bao nhieu so co 3 chu so ma tong co chu so cua moi so bang 4 . co tat ca bao nhieu so thoa man?

Bai 1 : 

a) Tim abcd biet : a x bcd = 1001                 b) Tim ab ; biet ab x aba = abab

Bai 2 Tim so co hai chu so, biet rang neu viet them chu so 6 vao ben trai so da cho thi duoc so moi gap 7 lan so cu.

Bai 3: Tim so co ba chu so, biet rang neu viet them chu so 3 vao ben trai so da cho thi duoc so moi gap 7 lan so do

Bai 4 :

a) Tim cac so a7b cung chia het  cho 5 va 9                 b) Tim cac aso 1ab cung chia het cho 5 va 3

Bai 5 : Tim so co hai chu so, biet rang so do chia cho hang don vi cua no thi duoc thuong la 6, du 5.

Bai 6: Cho so co hai chu so trong do chu so hang don vi la 7. Tim so da cho, biet rang neu chia so do cho tong cac chu so cua no thi duoc thuong la 5 va du 12.