Question

5．計(jì)算下面各題，能簡(jiǎn)算的要簡(jiǎn)算．
7.52×0.65÷0.752
1.6×7.5×1.25
（3.2+0.56）÷0.8
42÷28
2.4×8.6+7.5×8.6+0.86．

Answer 1

分析 ①運(yùn)用交換律可簡(jiǎn)便計(jì)算，
②運(yùn)用乘法交換律和結(jié)合律可簡(jiǎn)便計(jì)算，
③根據(jù)乘法分配律的變形可簡(jiǎn)便計(jì)算，
④根據(jù)除法的性質(zhì)可簡(jiǎn)便計(jì)算，
⑤先把2.4×8.6+7.5×8.6變成24×0.86+75×0.86，再逆用乘法分配律可簡(jiǎn)便計(jì)算．

解答 解：①7.52×0.65÷0.752
=7.52÷0.752×0.65
=10×0.65
=6.5

②1.6×7.5×1.25
=（2×0.8）×7.5×1.25
=（2×7.5）×（0.8×1.25）
=15×1
=15

③（3.2+0.56）÷0.8
=3.2÷0.8+0.56÷0.8
=4+0.7
=4.7

④42÷28
=42÷（7×4）
=42÷7÷4
=6÷4
=1.5

⑤2.4×8.6+7.5×8.6+0.86
=24×0.86+75×0.86+0.86
=（24+75+1）×0.86
=100×0.86
=86

點(diǎn)評(píng) 此題考查小數(shù)四則混合運(yùn)算順序和靈活運(yùn)用運(yùn)算定律，分析數(shù)據(jù)找到正確的計(jì)算方法．