Question

7．直接写出得数

$1\frac{3}{4}×\frac{2}{3}$=	$\frac{5}{7}×\frac{7}{8}×1\frac{2}{5}$=	$15\frac{3}{4}×99+15\frac{3}{4}$=	$11\frac{7}{8}-6\frac{1}{3}-1\frac{2}{3}$=
$\frac{1}{3}×\frac{6}{7}$=	$\frac{15}{16}×（\frac{2}{3}+\frac{2}{5}）$=	$8.6+3\frac{2}{5}+6\frac{3}{5}+1.4$=	$2.7+5\frac{4}{9}+7.3+3\frac{5}{9}$=

Answer 1

分析 根据分数和小数加减乘除法的计算方法进行计算．
$15\frac{3}{4}×99+15\frac{3}{4}$根据乘法分配律进行简算；
$11\frac{7}{8}-6\frac{1}{3}-1\frac{2}{3}$根据减法的性质进行简算；
$8.6+3\frac{2}{5}+6\frac{3}{5}+1.4$、$2.7+5\frac{4}{9}+7.3+3\frac{5}{9}$根据加法交换律和结合律进行简算．

解答 解：

$1\frac{3}{4}×\frac{2}{3}$=$\frac{7}{6}$	$\frac{5}{7}×\frac{7}{8}×1\frac{2}{5}$=$\frac{7}{8}$	$15\frac{3}{4}×99+15\frac{3}{4}$=1575	$11\frac{7}{8}-6\frac{1}{3}-1\frac{2}{3}$=3$\frac{7}{8}$
$\frac{1}{3}×\frac{6}{7}$=$\frac{2}{7}$	$\frac{15}{16}×（\frac{2}{3}+\frac{2}{5}）$=1	$8.6+3\frac{2}{5}+6\frac{3}{5}+1.4$=20	$2.7+5\frac{4}{9}+7.3+3\frac{5}{9}$=19

点评 口算时，注意运算符号和数据，然后再进一步计算．