a)10=5x2 sau 10x1
70=7x10
520=52x10
600=60x10 sau 6x100
320=32x10
800=80x10 sau 8x100
3450=345x100
2500=250x100 sau 25x1000
b)100=10x10
900=90x10 sau 9x100
1200=12x1000 sau 120x10
1000=10x100
6300=63x100 sau 630 x10
5000=50x100 sau 500x10
6400=64x100 sau 640x10
9000=9x1000 sau 900x10