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一、口算。
$20 - 6.9 =$
$0.23×0.3 =$
$4.5 - 3.05 =$
$2.2÷0.5 =$
$\frac{39}{10} - \frac{5}{6} =$
$\frac{11}{15} - \frac{2}{3} =$
$\frac{11}{12} - \frac{1}{2} =$
$\frac{5}{11} + \frac{7}{11} =$
$20 - 6.9 =$
13.1
$1.5×4 =$6
$3.86 + 7.24 =$11.1
$0.23×0.3 =$
0.069
$5.4 + 2.34 =$7.74
$5.1÷17 =$0.3
$4.5 - 3.05 =$
1.45
$12.6÷60 =$0.21
$1.86 + 1.75 =$3.61
$2.2÷0.5 =$
4.4
$2.01 + 0.9 =$2.91
$0.35×6 =$2.1
$\frac{39}{10} - \frac{5}{6} =$
$\frac{46}{15}$
$\frac{3}{4} - \frac{1}{10} =$$\frac{13}{20}$
$\frac{1}{2} + \frac{3}{5} =$$\frac{11}{10}$
$\frac{11}{15} - \frac{2}{3} =$
$\frac{1}{15}$
$\frac{5}{12} + \frac{1}{8} =$$\frac{13}{24}$
$\frac{6}{5} - \frac{9}{10} =$$\frac{3}{10}$
$\frac{11}{12} - \frac{1}{2} =$
$\frac{5}{12}$
$\frac{3}{4} + \frac{4}{7} =$$\frac{37}{28}$
$\frac{2}{5} + \frac{3}{10} =$$\frac{7}{10}$
$\frac{5}{11} + \frac{7}{11} =$
$\frac{12}{11}$
$\frac{5}{6} - \frac{5}{7} =$$\frac{5}{42}$
$\frac{3}{4} + \frac{7}{12} =$$\frac{4}{3}$
答案
一、13.1 6 11.1
0.069 7.74 0.3
1.45 0.21 3.61
4.4 2.91 2.1
$\frac{46}{15} \frac{13}{20} \frac{11}{10}$
$\frac{1}{15} \frac{13}{24} \frac{3}{10}$
$\frac{5}{12} \frac{37}{28} \frac{7}{10}$
$\frac{12}{11} \frac{5}{42} \frac{4}{3}$
0.069 7.74 0.3
1.45 0.21 3.61
4.4 2.91 2.1
$\frac{46}{15} \frac{13}{20} \frac{11}{10}$
$\frac{1}{15} \frac{13}{24} \frac{3}{10}$
$\frac{5}{12} \frac{37}{28} \frac{7}{10}$
$\frac{12}{11} \frac{5}{42} \frac{4}{3}$
二、计算下面各图形的表面积和体积。
答案
二、表面积：$\frac{5}{3} × \frac{5}{3} × 6 = \frac{50}{3} (cm^{2})$
体积：$\frac{5}{3} × \frac{5}{3} × \frac{5}{3} = \frac{125}{27} (cm^{3})$
表面积：$3 × 3 × 6 - 1 × 1 × 2 + 1 × 3 × 4 = 64 (cm^{2})$
体积：$3 × 3 × 3 - 1 × 1 × 3 = 24 (cm^{3})$
体积：$\frac{5}{3} × \frac{5}{3} × \frac{5}{3} = \frac{125}{27} (cm^{3})$
表面积：$3 × 3 × 6 - 1 × 1 × 2 + 1 × 3 × 4 = 64 (cm^{2})$
体积：$3 × 3 × 3 - 1 × 1 × 3 = 24 (cm^{3})$
