4,2,4,5,3,9,4,5,18这组数的中位数是 .
3: ==15÷ = ×= (小数).
5÷20==4: = :12= %= (填小数)
÷20=12: ==0.8= %.
= : =15÷ ==0.6.
4÷5==== ÷80.