Question

2．口算

$\frac{13}{19}$÷$\frac{39}{38}$=	（$\frac{1}{2}$-$\frac{1}{3}$）×6=	12÷$\frac{1}{4}$=	$\frac{1}{7}$+$\frac{6}{7}$×7=
$\frac{5}{6}$×$\frac{8}{15}$=	$\frac{3}{4}$+0.8=	0.8﹕1.2=	$\frac{1}{3}$﹕$\frac{2}{5}$=

Answer 1

分析 根據(jù)分?jǐn)?shù)加法、分?jǐn)?shù)減法、分?jǐn)?shù)乘法、分?jǐn)?shù)除法的計(jì)數(shù)法則，依次進(jìn)行解答即可；其中比的前項(xiàng)除以后項(xiàng)所得的商就是比值．

解答 解：

$\frac{13}{19}$÷$\frac{39}{38}$=$\frac{2}{3}$	（$\frac{1}{2}$-$\frac{1}{3}$）×6=1	12÷$\frac{1}{4}$=48	$\frac{1}{7}$+$\frac{6}{7}$×7=6$\frac{1}{7}$
$\frac{5}{6}$×$\frac{8}{15}$=$\frac{4}{9}$	$\frac{3}{4}$+0.8=1.55	0.8﹕1.2=$\frac{2}{3}$	$\frac{1}{3}$﹕$\frac{2}{5}$=$\frac{5}{6}$

點(diǎn)評(píng) 靈活掌握分?jǐn)?shù)加法、分?jǐn)?shù)減法、分?jǐn)?shù)乘法、分?jǐn)?shù)除法的計(jì)數(shù)法則，是解答此題的關(guān)鍵．