40×20=(4×10)×(2×10)=(4×2)×(10×10)=8×100=800
0.4×0.2=(4×0.1)×(2×0.1)=( × )×( × )= ×
=(4× )×(2× )=( × )×( × )= ×
﹣0.5= +3= ×= 0.8×=
0.23+177%= 2.5×40= 1÷= ×÷×=
101×25= ×0.5= ×= 5+= 2.5× =
3.2÷8= 1.25- = 5× ÷5÷ = 1.25× ×0.8=
× = 1÷ = ÷ = 45×102=