123×30=3690 123×2=246 3690+246=3936
45×12=540(元)这一步算的是:
540×5=2700(元)这一步算的是:
0.1-0.01= 6.8÷10%= 3.6÷0.12= 398÷42≈
0.22= × = 24÷ = ×4÷ ×4=