Question

1．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=	$\frac{8}{21}$×$\frac{7}{16}$=	$\frac{1}{20}$×$\frac{2}{3}$=

Answer 1

分析 根據(jù)分數(shù)乘法的計算方法計算，即分母和分母相乘的積做分母，分子和分子相乘的積做分子，能約分的要先約分再計算．

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×$\frac{3}{20}$=$\frac{3}{20}$	$\frac{2}{5}$×$\frac{15}{4}$=$\frac{3}{2}$	$\frac{4}{17}$×34=8	$\frac{8}{21}$×$\frac{7}{16}$=$\frac{1}{6}$	$\frac{1}{20}$×$\frac{2}{3}$=$\frac{1}{30}$．

點評 本題考查了基本的分數(shù)乘法的計算，注意能約分的要先約分再乘，結(jié)果要化成最簡分數(shù)．