《2025年口算题卡升级练六年级数学上册人教版》

4 计算下面各题,能简便计算的要简便计算。
$\frac {1}{2}÷\frac {5}{8}+\frac {1}{4}×\frac {3}{5}$
$\frac {3}{4}×\frac {2}{5}+\frac {1}{4}÷\frac {5}{2}$
$\frac {1}{4}-\frac {10}{21}×\frac {7}{20}÷\frac {5}{6}$
$(\frac {3}{8}-\frac {1}{4})÷\frac {3}{8}$
$\frac {3}{8}÷(\frac {3}{8}-\frac {1}{4})$
$\frac {5}{6}×4÷(\frac {7}{8}+\frac {2}{3})$

答案： 1.
$\;\;\;\;\frac{1}{2} ÷ \frac{5}{8} + \frac{1}{4} × \frac{3}{5}$
$= \frac{1}{2} × \frac{8}{5} + \frac{1}{4} × \frac{3}{5}$
$= \frac{4}{5} + \frac{3}{20}$
$= \frac{16}{20} + \frac{3}{20}$
$= \frac{19}{20}$
2.
$\;\;\;\;\frac{3}{4} × \frac{2}{5} + \frac{1}{4} ÷ \frac{5}{2}$
$= \frac{3}{4} × \frac{2}{5} + \frac{1}{4} × \frac{2}{5}$
$= (\frac{3}{4} + \frac{1}{4}) × \frac{2}{5}$
$= 1 × \frac{2}{5}$
$= \frac{2}{5}$
3.
$\;\;\;\;\frac{1}{4} - \frac{10}{21} × \frac{7}{20} ÷ \frac{5}{6}$
$= \frac{1}{4} - \frac{10}{21} × \frac{7}{20} × \frac{6}{5}$
$= \frac{1}{4} - \frac{1}{5}$
$= \frac{5}{20} - \frac{4}{20}$
$= \frac{1}{20}$
4.
$\;\;\;\;(\frac{3}{8} - \frac{1}{4}) ÷ \frac{3}{8}$
$= (\frac{3}{8} - \frac{2}{8}) × \frac{8}{3}$
$= \frac{1}{8} × \frac{8}{3}$
$= \frac{1}{3}$
5.
$\;\;\;\;\frac{3}{8} ÷ (\frac{3}{8} - \frac{1}{4})$
$= \frac{3}{8} ÷ (\frac{3}{8} - \frac{2}{8})$
$= \frac{3}{8} ÷ \frac{1}{8}$
$= 3$
6.
$\;\;\;\;\frac{5}{6} × 4 ÷ (\frac{7}{8} + \frac{2}{3})$
$= \frac{5}{6} × 4 ÷ (\frac{21}{24} + \frac{16}{24})$
$= \frac{5}{6} × 4 × \frac{24}{37}$
$= \frac{20}{6} × \frac{24}{37}$
$= \frac{80}{37}$

5 列式计算。
① 一个数加上它的$\frac {1}{5}$等于 600 的$\frac {4}{5}$,这个数是多少?
② $\frac {2}{3}与\frac {3}{5}$的积比 25 的$\frac {1}{5}$少多少?
③ $\frac {9}{14}除以\frac {4}{5}的商乘\frac {8}{15}$,积是多少?
④ 一个数的$\frac {4}{15}是\frac {8}{9}的\frac {1}{6}$,求这个数。

答案： ①解：设这个数是$x$。
$x+\frac{1}{5}x = 600×\frac{4}{5}$
$\frac{6}{5}x=480$
$x=480÷\frac{6}{5}$
$x=400$
②$25×\frac{1}{5}-\frac{2}{3}×\frac{3}{5}$
$=5 - \frac{2}{5}$
$=4\frac{3}{5}$
③$\frac{9}{14}÷\frac{4}{5}×\frac{8}{15}$
$=\frac{9}{14}×\frac{5}{4}×\frac{8}{15}$
$=\frac{3}{7}$
④解：设这个数是$x$。
$\frac{4}{15}x=\frac{8}{9}×\frac{1}{6}$
$\frac{4}{15}x=\frac{4}{27}$
$x=\frac{4}{27}÷\frac{4}{15}$
$x=\frac{5}{9}$