Question

11．計算下面各題．（能簡算的要簡算）．
$\frac{3}{4}$×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逆用乘法分配律可簡便計算，
②先把百分數變成分數，再用乘法交換律可簡便計算，
③先把百分數變成小數，再逆用乘法分配律簡算．

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

點評 此題考查小數、分數、百分數四則混合運算順序和靈活運用運算定律，分析數據找到正確的計算方法．