Question

8．直接写得数

$\frac{4}{5}$+$\frac{1}{5}$=	$\frac{3}{4}$_$\frac{1}{4}$=	$\frac{2}{5}$×2=	$\frac{3}{7}$×$\frac{1}{3}$=
$\frac{1}{2}$÷60%=	$\frac{5}{9}$×$\frac{3}{5}$=	$\frac{4}{9}$÷4=	$\frac{3}{5}$÷$\frac{1}{5}$=
12×$\frac{3}{4}$=	$\frac{21}{25}$÷42=	2-$\frac{3}{7}$=	3$\frac{1}{4}$+1.75=
$\frac{4}{11}$÷4=	1÷$\frac{3}{2}$×$\frac{2}{3}$=

Answer 1

分析 根据分数的加、减、乘、除法的计算方法．

解答 解：$\frac{4}{5}+\frac{1}{5}$=1            $\frac{3}{4}-\frac{1}{4}=\frac{1}{2}$          $\frac{2}{5}×2=\frac{4}{5}$              $\frac{3}{7}×\frac{1}{3}=\frac{1}{7}$
$\frac{1}{2}÷60%=\frac{5}{6}$           $\frac{5}{9}×\frac{3}{5}=\frac{1}{3}$          $\frac{4}{9}÷4=\frac{1}{9}$               $\frac{3}{5}÷\frac{1}{5}=3$
$12×\frac{3}{4}=9$             $\frac{21}{25}÷42=\frac{1}{50}$        $2-\frac{3}{7}=1\frac{4}{7}$              $3\frac{1}{4}+1.75=5$
$\frac{4}{11}÷4=\frac{1}{11}$           $1÷\frac{3}{2}×\frac{2}{3}=\frac{4}{9}$

点评 口算题要看准运算符号和数据，灵活计算．