《2025年口算训练六年级数学上册人教版双色升级版》

2. 用合理的方法计算下列各题。
$\frac {13}{18}×\frac {2}{3}+\frac {2}{3}×\frac {5}{18}$ $\frac {4}{5}×1\frac {2}{5}-\frac {2}{5}×0.8$ $6.5×2\frac {2}{3}×\frac {9}{13}$
$\frac {7}{13}-\frac {2}{15}×\frac {7}{13}$ $34÷21×\frac {7}{51}$ $\frac {2}{5}×(\frac {2}{5}+2\frac {1}{2})$
$49\frac {48}{49}×12$ $46×(\frac {5}{23}-\frac {5}{32})×64$ $\frac {11}{17}×\frac {13}{29}+\frac {16}{17}×\frac {11}{29}$

答案： 解析：本题可根据四则运算定律，如乘法分配律、乘法交换律、乘法结合律等对各算式进行简便计算。
答案：
$\frac {13}{18}×\frac {2}{3}+\frac {2}{3}×\frac {5}{18}$
$=\frac {2}{3}×(\frac {13}{18}+\frac {5}{18})$
$=\frac {2}{3}×1$
$=\frac {2}{3}$
$\frac {4}{5}×1\frac {2}{5}-\frac {2}{5}×0.8$
$=\frac {4}{5}×\frac {7}{5}-\frac {2}{5}×\frac {4}{5}$
$=\frac {4}{5}×(\frac {7}{5}-\frac {2}{5})$
$=\frac {4}{5}×1$
$=\frac {4}{5}$
$6.5×2\frac {2}{3}×\frac {9}{13}$
$=6.5×\frac {8}{3}×\frac {9}{13}$
$=\frac {13}{2}×\frac {8}{3}×\frac {9}{13}$
$=(\frac {13}{2}×\frac {9}{13})×\frac {8}{3}$
$=\frac {9}{2}×\frac {8}{3}$
$=12$
$\frac {7}{13}-\frac {2}{15}×\frac {7}{13}$
$=\frac {7}{13}×(1 - \frac {2}{15})$
$=\frac {7}{13}×\frac {13}{15}$
$=\frac {7}{15}$
$34÷21×\frac {7}{51}$
$=34×\frac {1}{21}×\frac {7}{51}$
$=34×\frac {7}{21×51}$
$=\frac {2}{9}$
$\frac {2}{5}×(\frac {2}{5}+2\frac {1}{2})$
$=\frac {2}{5}×(\frac {2}{5}+\frac {5}{2})$
$=\frac {2}{5}×\frac {2}{5}+\frac {2}{5}×\frac {5}{2}$
$=\frac {4}{25}+1$
$=1\frac {4}{25}$
$49\frac {48}{49}×12$
$=(50 - \frac {1}{49})×12$
$=50×12 - \frac {1}{49}×12$
$=600 - \frac {12}{49}$
$=599\frac {37}{49}$
$46×(\frac {5}{23}-\frac {5}{32})×64$
$=46×\frac {5}{23}×64 - 46×\frac {5}{32}×64$
$=10×64 - 5×46×2$
$=640 - 460$
$=180$
$\frac {11}{17}×\frac {13}{29}+\frac {16}{17}×\frac {11}{29}$
$=\frac {11}{17}×\frac {13}{29}+\frac {11}{17}×\frac {16}{29}$
$=\frac {11}{17}×(\frac {13}{29}+\frac {16}{29})$
$=\frac {11}{17}×1$
$=\frac {11}{17}$

3. 看图列式计算。
1. $12 × \frac{1}{2} = 6$
2. $125 × (1 + \frac{1}{5}) = 150$（m）
3. $270 × (1 - \frac{3}{8} - \frac{1}{9}) = 122.5$（kg）

答案： 1. $12 × \frac{1}{2} = 6$
2. $125 × (1 + \frac{1}{5}) = 150$（m）
3. $270 × (1 - \frac{3}{8} - \frac{1}{9}) = 122.5$（kg）