Question

11．计算下面各题．（能简算的要简算）．
$\frac{3}{4}$×40%+$\frac{3}{4}$×60%     
$\frac{5}{8}$×$\frac{1}{9}$×80%     
$\frac{3}{5}$×30%+$\frac{7}{10}$×0.6-60%

Answer 1

分析 ①逆用乘法分配律可简便计算，
②先把百分数变成分数，再用乘法交换律可简便计算，
③先把百分数变成小数，再逆用乘法分配律简算．

解答 解：①$\frac{3}{4}$×40%+$\frac{3}{4}$×60%
=$\frac{3}{4}$×（40%+60%）
=$\frac{3}{4}$×1
=$\frac{3}{4}$

②$\frac{5}{8}$×$\frac{1}{9}$×80%
=$\frac{5}{8}$×$\frac{1}{9}$×$\frac{4}{5}$
=$\frac{5}{8}$×$\frac{4}{5}$×$\frac{1}{9}$
=$\frac{1}{2}$×$\frac{1}{9}$
=$\frac{1}{18}$

③$\frac{3}{5}$×30%+$\frac{7}{10}$×0.6-60%
=0.6×$\frac{3}{10}$$+\frac{7}{10}$×0.6-0.6
=0.6×（$\frac{3}{10}$$+\frac{7}{10}$-1）
=0.6×0
=0

点评 此题考查小数、分数、百分数四则混合运算顺序和灵活运用运算定律，分析数据找到正确的计算方法．