×4= ÷3= ×4= 5÷=
×= ÷= 2.4×= 0.6×=
÷= += 2﹣= ÷6=
×3= ×13= 15×= 18×=
×= ×= ×= ×=
+=
=
等级
优
良
轻微污染
占全月天数的几分之几
0.6+4.5= ﹣ = 2÷ = 2.5:6=
125%×8= 18÷54= 0.5×2.4= : =