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四、用运算律进行简便计算。（每题3分，共18分）
2.1÷0.5÷0.6
0.75×18÷0.15
4.5×10.2
44.4×0.25
3.87×7.9+3.87×2.1
18-600÷(60×2.5)
2.1÷0.5÷0.6
0.75×18÷0.15
4.5×10.2
44.4×0.25
3.87×7.9+3.87×2.1
18-600÷(60×2.5)
答案
1. 7
2. 90
3. 45.9
4. 11.1
5. 38.7
6. 14
2. 90
3. 45.9
4. 11.1
5. 38.7
6. 14
五、计算下面各题,能用简便算法的就用简便算法。(每题3分,共18分)
$\frac{10}{11} + \frac{2}{5} + \frac{1}{11}$
$\frac{17}{16} - \frac{1}{4} + \frac{3}{8}$
$\frac{13}{24} + \frac{2}{3} - \frac{5}{6}$
$\frac{3}{7} + \frac{7}{9} - \frac{3}{7}$
$\frac{12}{7} - \frac{4}{9} - \frac{5}{9} + \frac{2}{7}$
$\frac{37}{25} - \frac{3}{11} - (\frac{8}{11} - \frac{13}{25})$
$\frac{10}{11} + \frac{2}{5} + \frac{1}{11}$
$\frac{17}{16} - \frac{1}{4} + \frac{3}{8}$
$\frac{13}{24} + \frac{2}{3} - \frac{5}{6}$
$\frac{3}{7} + \frac{7}{9} - \frac{3}{7}$
$\frac{12}{7} - \frac{4}{9} - \frac{5}{9} + \frac{2}{7}$
$\frac{37}{25} - \frac{3}{11} - (\frac{8}{11} - \frac{13}{25})$
答案
1. $1\frac{2}{5}$
2. $\frac{19}{16}$
3. $\frac{3}{8}$
4. $\frac{7}{9}$
5. 1
6. 1
2. $\frac{19}{16}$
3. $\frac{3}{8}$
4. $\frac{7}{9}$
5. 1
6. 1
计算: $1\frac{4}{5} + 3\frac{4}{5} + 5\frac{4}{5} + 7\frac{4}{5} + 9\frac{4}{5} + 1$。(共5分)
答案
$1\frac{4}{5} + 3\frac{4}{5} + 5\frac{4}{5} + 7\frac{4}{5} + 9\frac{4}{5}+1$
$=1\frac{4}{5} + 3\frac{4}{5} + 5\frac{4}{5} + 7\frac{4}{5} + 9\frac{4}{5}+(\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5})$
$=(1\frac{4}{5}+\frac{1}{5})+(3\frac{4}{5}+\frac{1}{5})+(5\frac{4}{5}+\frac{1}{5})+(7\frac{4}{5}+\frac{1}{5})+(9\frac{4}{5}+\frac{1}{5})$
$=2+4+6+8+10$
$=30$
$=1\frac{4}{5} + 3\frac{4}{5} + 5\frac{4}{5} + 7\frac{4}{5} + 9\frac{4}{5}+(\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5})$
$=(1\frac{4}{5}+\frac{1}{5})+(3\frac{4}{5}+\frac{1}{5})+(5\frac{4}{5}+\frac{1}{5})+(7\frac{4}{5}+\frac{1}{5})+(9\frac{4}{5}+\frac{1}{5})$
$=2+4+6+8+10$
$=30$
