Question

13．

口算 $\frac{5}{9}$×15=	$\frac{3}{5}$×2=	$\frac{1}{4}$×$\frac{4}{5}$=	$\frac{1}{9}$×$\frac{3}{7}$=	$\frac{7}{12}$×$\frac{3}{4}$=	1×$\frac{3}{20}$=
$\frac{2}{5}$×$\frac{15}{4}$=	$\frac{4}{17}$×34=	$\frac{8}{21}$×$\frac{7}{16}$=	$\frac{1}{20}$×$\frac{2}{3}$=	$\frac{3}{4}$×$\frac{1}{5}$=	$\frac{5}{6}$×$\frac{2}{15}$=
$\frac{6}{11}$×$\frac{1}{12}$=	$\frac{3}{22}$×$\frac{11}{13}$=	$\frac{7}{6}$×24=	$\frac{4}{7}$×$\frac{3}{8}$=	$\frac{13}{15}$×30=	28×$\frac{7}{24}$=
$\frac{5}{6}$×$\frac{3}{7}$=	$\frac{15}{17}$×$\frac{17}{15}$=

Answer 1

分析 根據(jù)分?jǐn)?shù)乘以分?jǐn)?shù)的計算方法進(jìn)行計算即可．

解答 解：

$\frac{5}{9}$×15=$\frac{25}{3}$	$\frac{3}{5}$×2=$\frac{6}{5}$	$\frac{1}{4}$×$\frac{4}{5}$=$\frac{1}{5}$	$\frac{1}{9}$×$\frac{3}{7}$=$\frac{1}{21}$	$\frac{7}{12}$×$\frac{3}{4}$=$\frac{7}{16}$	1×$\frac{3}{20}$=$\frac{3}{20}$
$\frac{2}{5}$×$\frac{15}{4}$=1.5	$\frac{4}{17}$×34=8	$\frac{8}{21}$×$\frac{7}{16}$=$\frac{1}{6}$	$\frac{1}{20}$×$\frac{2}{3}$=$\frac{1}{30}$	$\frac{3}{4}$×$\frac{1}{5}$=$\frac{3}{20}$	$\frac{5}{6}$×$\frac{2}{15}$=$\frac{1}{9}$
$\frac{6}{11}$×$\frac{1}{12}$=$\frac{1}{22}$	$\frac{3}{22}$×$\frac{11}{13}$=$\frac{3}{26}$	$\frac{7}{6}$×24=28	$\frac{4}{7}$×$\frac{3}{8}$=$\frac{3}{14}$	$\frac{13}{15}$×30=26	28×$\frac{7}{24}$=$\frac{49}{6}$
$\frac{5}{6}$×$\frac{3}{7}$=$\frac{5}{14}$	$\frac{15}{17}$×$\frac{17}{15}$=1

點評 掌握分?jǐn)?shù)乘以分?jǐn)?shù)的方法是解答本題的關(guān)鍵．計算的結(jié)果如果是分?jǐn)?shù)，用最簡分?jǐn)?shù)表示．