Question

7．計(jì)算下面各題（能簡(jiǎn)算的要簡(jiǎn)算）
（$\frac{4}{5}$+$\frac{1}{4}$）÷$\frac{7}{3}$-$\frac{1}{4}$
$\frac{3}{8}$×$\frac{1}{4}$÷$\frac{3}{8}$×$\frac{1}{4}$
[64-（$\frac{7}{3}$+$\frac{1}{4}$）×24]÷$\frac{1}{4}$
 $\frac{3}{5}$-$\frac{1}{12}$÷$\frac{5}{12}$×$\frac{12}{5}$．

Answer 1

分析 ①（$\frac{4}{5}$+$\frac{1}{4}$）÷$\frac{7}{3}$-$\frac{1}{4}$，先算括號(hào)里面的加法，再算除法，最后算減法；
②$\frac{3}{8}$×$\frac{1}{4}$÷$\frac{3}{8}$×$\frac{1}{4}$，先算$\frac{3}{8}÷\frac{3}{8}$，再算乘法；
③[64-（$\frac{7}{3}$+$\frac{1}{4}$）×24]÷$\frac{1}{4}$，先算小括號(hào)里面的根據(jù)乘法的分配律計(jì)算，再算中括號(hào)里面的，最后算除法；
④$\frac{3}{5}$-$\frac{1}{12}$÷$\frac{5}{12}$×$\frac{12}{5}$，先算除法、乘法，再算減法．

解答 解：①（$\frac{4}{5}$+$\frac{1}{4}$）÷$\frac{7}{3}$-$\frac{1}{4}$
=$\frac{21}{20}÷\frac{7}{3}-\frac{1}{4}$
=$\frac{21}{20}×\frac{3}{7}-\frac{1}{4}$
=$\frac{9}{20}-\frac{1}{4}$
=$\frac{4}{20}$
=$\frac{1}{5}$；

②$\frac{3}{8}$×$\frac{1}{4}$÷$\frac{3}{8}$×$\frac{1}{4}$
=$\frac{3}{8}×\frac{8}{3}×\frac{1}{4}×\frac{1}{4}$
=$1×\frac{1}{16}$
=$\frac{1}{16}$；

③[64-（$\frac{7}{3}$+$\frac{1}{4}$）×24]÷$\frac{1}{4}$
=[64-（$\frac{7}{3}$×24+$\frac{1}{4}$×24）]$÷\frac{1}{4}$
=[64-62]$÷\frac{1}{4}$
=2×4
=8；

④$\frac{3}{5}$-$\frac{1}{12}$÷$\frac{5}{12}$×$\frac{12}{5}$
=$\frac{3}{5}-\frac{1}{12}×\frac{12}{5}×\frac{12}{5}$
=$\frac{3}{5}-\frac{12}{25}$
=$\frac{15}{25}-\frac{12}{25}$
=$\frac{3}{25}$．

點(diǎn)評(píng) 此題考查的目的是理解掌握分?jǐn)?shù)四則混合運(yùn)算的順序以及它們的計(jì)算法則，并且能夠正確熟練地進(jìn)行計(jì)算．