分子、分母是质数的分数是最简分数 .
12÷ = :20==0.8= %
将分数1写成两个数相除的式子:1 .
:16=15÷ == %= (填小数)
÷ = :16=5÷ = %=0.25.
0.8=12÷ = :10= %