a×2简写做2a,则a×a×a×a可简写做4a. .
=24: = ÷20= %
:20=20: == %= (最后一空填小数)
9÷ ==37.5%=24: =.
3: ==24÷ = %=0.8.
a除以b的商是2,a就是b的2倍. .