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1. $25×6×4= $
答案
600
解析
25×4×6=100×6=600
2. $\frac {7}{8}×\frac {5}{12}×\frac {8}{7}= $
答案
$\frac{5}{12}$
解析
$\frac{7}{8} × \frac{5}{12} × \frac{8}{7} = \frac{7}{8} × \frac{8}{7} × \frac{5}{12} = 1 × \frac{5}{12} = \frac{5}{12}$
3. $1.25×6.4×8= $
答案
64
解析
$1.25×6.4×8$
$=1.25×8×6.4$
$=10×6.4$
$=64$
$=1.25×8×6.4$
$=10×6.4$
$=64$
4. $101×34 - 34= $
答案
3 400
解析
$101×34 - 34$
$=(101 - 1)×34$
$=100×34$
$=3400$
$=(101 - 1)×34$
$=100×34$
$=3400$
5. $1200÷25÷4= $
答案
12
解析
1200÷25÷4=1200÷(25×4)=1200÷100=12
6. $3.2×125= $
答案
400
解析
$3.2×125$
$=0.4×8×125$
$=0.4×(8×125)$
$=0.4×1000$
$=400$
$=0.4×8×125$
$=0.4×(8×125)$
$=0.4×1000$
$=400$
7. $15×(\frac {7}{8}×\frac {4}{15})= $
答案
$\frac{7}{2}$
解析
$15×\left(\frac{7}{8}×\frac{4}{15}\right)$
$=15×\frac{4}{15}×\frac{7}{8}$
$=4×\frac{7}{8}$
$=\frac{7}{2}$
$=15×\frac{4}{15}×\frac{7}{8}$
$=4×\frac{7}{8}$
$=\frac{7}{2}$
8. $0.2×3.169×50= $
答案
31.69
解析
0.2×50×3.169=10×3.169=31.69
9. $3.2×1.1 - 3.2= $
答案
0.32
解析
$3.2×1.1 - 3.2$
$=3.2×(1.1 - 1)$
$=3.2×0.1$
$=0.32$
$=3.2×(1.1 - 1)$
$=3.2×0.1$
$=0.32$
10. $18×7 + 12×7= $
答案
210
解析
$(18 + 12)×7 = 30×7 = 210$
11. $25×5.5×0.4×2$
答案
110
解析
$25×5.5×0.4×2$
$=(25×0.4)×(5.5×2)$
$=10×11$
$=110$
$=(25×0.4)×(5.5×2)$
$=10×11$
$=110$
12. $86.4×3.2 - 6.4×3.2$
答案
256
解析
$86.4×3.2 - 6.4×3.2$
$=(86.4 - 6.4)×3.2$
$=80×3.2$
$=256$
$=(86.4 - 6.4)×3.2$
$=80×3.2$
$=256$
13. $\frac {11}{27}×1\frac {11}{42}×4\frac {10}{11}$
答案
$\frac{53}{21}$
解析
$\frac{11}{27} × 1\frac{11}{42} × 4\frac{10}{11}$
$=\frac{11}{27} × \frac{53}{42} × \frac{54}{11}$
$=\frac{11}{27} × \frac{54}{11} × \frac{53}{42}$
$=2 × \frac{53}{42}$
$=\frac{53}{21}$
$=\frac{11}{27} × \frac{53}{42} × \frac{54}{11}$
$=\frac{11}{27} × \frac{54}{11} × \frac{53}{42}$
$=2 × \frac{53}{42}$
$=\frac{53}{21}$
14. $\frac {7}{9}÷2\frac {1}{5}+\frac {2}{9}×\frac {5}{11}$
答案
$\frac{5}{11}$
解析
$\frac{7}{9}÷2\frac{1}{5}+\frac{2}{9}×\frac{5}{11}$
$=\frac{7}{9}÷\frac{11}{5}+\frac{2}{9}×\frac{5}{11}$
$=\frac{7}{9}×\frac{5}{11}+\frac{2}{9}×\frac{5}{11}$
$=(\frac{7}{9}+\frac{2}{9})×\frac{5}{11}$
$=1×\frac{5}{11}$
$=\frac{5}{11}$
$=\frac{7}{9}÷\frac{11}{5}+\frac{2}{9}×\frac{5}{11}$
$=\frac{7}{9}×\frac{5}{11}+\frac{2}{9}×\frac{5}{11}$
$=(\frac{7}{9}+\frac{2}{9})×\frac{5}{11}$
$=1×\frac{5}{11}$
$=\frac{5}{11}$
15. $13×(\frac {1}{13}-\frac {1}{15})×15$
答案
2
解析
$13×(\frac{1}{13}-\frac{1}{15})×15$
$=13×15×(\frac{1}{13}-\frac{1}{15})$
$=13×15×\frac{1}{13}-13×15×\frac{1}{15}$
$=15 - 13$
$=2$
$=13×15×(\frac{1}{13}-\frac{1}{15})$
$=13×15×\frac{1}{13}-13×15×\frac{1}{15}$
$=15 - 13$
$=2$
16. $333×125 + 111×625$
答案
111 000
解析
$333×125 + 111×625$
$=111×3×125 + 111×625$
$=111×375 + 111×625$
$=111×(375 + 625)$
$=111×1000$
$=111000$
$=111×3×125 + 111×625$
$=111×375 + 111×625$
$=111×(375 + 625)$
$=111×1000$
$=111000$
17. $(\frac {1}{2}×1\frac {1}{2})×(\frac {2}{3}×1\frac {1}{3})×(\frac {3}{4}×1\frac {1}{4})×... ×(\frac {98}{99}×1\frac {1}{99})×(\frac {99}{100}×1\frac {1}{100})$
答案
$\frac{101}{200}$
解析
$\begin{aligned}&(\frac{1}{2} × 1\frac{1}{2}) × (\frac{2}{3} × 1\frac{1}{3}) × (\frac{3}{4} × 1\frac{1}{4}) × \cdots × (\frac{98}{99} × 1\frac{1}{99}) × (\frac{99}{100} × 1\frac{1}{100})\\=&\left(\frac{1}{2} × \frac{3}{2}\right) × \left(\frac{2}{3} × \frac{4}{3}\right) × \left(\frac{3}{4} × \frac{5}{4}\right) × \cdots × \left(\frac{98}{99} × \frac{100}{99}\right) × \left(\frac{99}{100} × \frac{101}{100}\right)\\=&\left(\frac{1}{2} × \frac{2}{3} × \frac{3}{4} × \cdots × \frac{98}{99} × \frac{99}{100}\right) × \left(\frac{3}{2} × \frac{4}{3} × \frac{5}{4} × \cdots × \frac{100}{99} × \frac{101}{100}\right)\\=&\frac{1}{100} × \frac{101}{2}\\=&\frac{101}{200}\end{aligned}$
