从装有3个白球,2个黑球的口袋中任意摸出两球,全是白球的概率是 .
.
÷20== :15== (填小数)= %
= %= ÷20=0.35= :40.
0.75== ÷8= %= 成数.
3÷ =× =5: =1.25=.