一、口算。
0.15×30=
1.89÷0.1=
3.14×0.5²=
0.6×0.8=
1.3−1.03=
6.4÷0.08=
0.8+2.23=
6.3÷0.21=
5.25−2.52=
5.75−4.25=
477+333=
1.57÷3.14=
$\frac{2}{3} - \frac{5}{9} =$
$\frac{5}{12} + \frac{2}{3} =$
$\frac{2}{15} ÷ \frac{1}{6} =$
$\frac{14}{15} - \frac{2}{3} =$
$20 × \frac{5}{12} =$
$\frac{1}{4} × \frac{2}{7} =$
$\frac{7}{8} ÷ \frac{7}{16} =$
$\frac{3}{5} ÷ \frac{4}{5} =$
$\frac{7}{2} ÷ \frac{7}{6} =$
$3.6 × \frac{4}{9} =$
$\frac{3}{10} ÷ \frac{1}{10} =$
$\frac{3}{4} + \frac{2}{5} =$

0.15×30=4.5
1.89÷0.1=18.9
3.14×0.5²=0.785
0.6×0.8=0.48
1.3−1.03=0.27
6.4÷0.08=80
0.8+2.23=3.03
6.3÷0.21=30
5.25−2.52=2.73
5.75−4.25=1.5
477+333=810
1.57÷3.14=0.5
$\frac{2}{3} - \frac{5}{9} =\frac{1}{9}$
$\frac{5}{12} + \frac{2}{3} =\frac{13}{12}$
$\frac{2}{15} ÷ \frac{1}{6} =\frac{4}{5}$
$\frac{14}{15} - \frac{2}{3} =\frac{4}{15}$
$20 × \frac{5}{12} =\frac{25}{3}$
$\frac{1}{4} × \frac{2}{7} =\frac{1}{14}$
$\frac{7}{8} ÷ \frac{7}{16} =2$
$\frac{3}{5} ÷ \frac{4}{5} =\frac{3}{4}$
$\frac{7}{2} ÷ \frac{7}{6} =3$
$3.6 × \frac{4}{9} =\frac{8}{5}$
$\frac{3}{10} ÷ \frac{1}{10} =3$
$\frac{3}{4} + \frac{2}{5} =\frac{23}{20}$

二、计算下面各图形中涂色部分的周长和面积。
1.
2.

1. 周长:3.14×10÷2+10=25.7(cm)
面积:5×5=25(cm²)
2. 周长:3.14×2÷2+2×3.14×2÷4+2=8.28(dm)
面积:3.14×2²÷4-3.14×(2÷2)²÷2=1.57(dm²)