Question

10．脫式計(jì)算．

$\frac{1}{6}$+$\frac{1}{4}$-$\frac{1}{3}$	25×$\frac{2}{27}$×$\frac{3}{5}$	$\frac{3}{4}$×$\frac{8}{15}$×$\frac{10}{13}$
$\frac{3}{5}$×6×$\frac{25}{9}$	$\frac{9}{5}$×$\frac{2}{3}$×$\frac{35}{18}$	15×$\frac{25}{6}$×$\frac{4}{5}$．

Answer 1

分析 ①$\frac{1}{6}$+$\frac{1}{4}$-$\frac{1}{3}$，先通分，再按照同分母分?jǐn)?shù)的加、減法的計(jì)算法則計(jì)算；
②25×$\frac{2}{27}$×$\frac{3}{5}$，運(yùn)用乘法交換律、結(jié)合律簡(jiǎn)算；
③$\frac{3}{4}$×$\frac{8}{15}$×$\frac{10}{13}$，按照從左到右的順序計(jì)算；
④$\frac{3}{5}$×6×$\frac{25}{9}$，運(yùn)用乘法交換律、結(jié)合律簡(jiǎn)算；
⑤$\frac{9}{5}$×$\frac{2}{3}$×$\frac{35}{18}$，運(yùn)用乘法交換律、結(jié)合律簡(jiǎn)算；
⑥15×$\frac{25}{6}$×$\frac{4}{5}$．運(yùn)用乘法結(jié)合律簡(jiǎn)算．

解答 解：①$\frac{1}{6}$+$\frac{1}{4}$-$\frac{1}{3}$
=$\frac{2}{12}+\frac{3}{12}-\frac{4}{12}$
=$\frac{5}{12}-\frac{4}{12}$
=$\frac{1}{12}$；

②25×$\frac{2}{27}$×$\frac{3}{5}$
=$\frac{2}{27}×（25×\frac{3}{5}）$
=$\frac{2}{27}×9$
=$\frac{2}{3}$；

③$\frac{3}{4}$×$\frac{8}{15}$×$\frac{10}{13}$
=$\frac{2}{5}×\frac{10}{13}$
=$\frac{4}{13}$；

④$\frac{3}{5}$×6×$\frac{25}{9}$
=$6×（\frac{3}{5}×\frac{25}{9}）$
=$6×\frac{5}{3}$
=10；

⑤$\frac{9}{5}$×$\frac{2}{3}$×$\frac{35}{18}$=$\frac{2}{3}×（\frac{9}{5}×\frac{35}{18}）$
=$\frac{2}{3}×\frac{7}{2}$
=$\frac{7}{3}$；

⑥15×$\frac{25}{6}$×$\frac{4}{5}$
=$15×（\frac{25}{6}×\frac{4}{5}）$
=$15×\frac{10}{3}$
=50．

點(diǎn)評(píng) 此題考查的目的是理解掌握是四則混合運(yùn)算的順序以及它們的計(jì)算法則，并且能夠靈活選擇簡(jiǎn)便方法進(jìn)行計(jì)算．