Question

7．計(jì)算下面各題，注意運(yùn)用簡(jiǎn)便方法．
2.4-0.2÷5×60                      
0.25×6.8×40
5.52-0.55-0.45                       
0.49×7.2-7.2×0.39．

Answer 1

分析 ①先算乘除法再算減法；
②根據(jù)乘法交換律和結(jié)合律進(jìn)行簡(jiǎn)便計(jì)算；
③根據(jù)減法的性質(zhì)進(jìn)行簡(jiǎn)便計(jì)算；
④根據(jù)乘法分配律進(jìn)行簡(jiǎn)便計(jì)算．

解答 解：①2.4-0.2÷5×60
=2.4-0.04×60
=2.4-2.4
=0

 ②0.25×6.8×40
=（0.25×40）×6.8
=10×6.8
=68

③5.52-0.55-0.45
=5.52-（0.55+0.45）
=5.52-1
=4.52
              
④0.49×7.2-7.2×0.39
=7.2×（0.49-0.39）
=7.2×0.1
=0.72

點(diǎn)評(píng) 考查了運(yùn)算定律與簡(jiǎn)便運(yùn)算，四則混合運(yùn)算．注意運(yùn)算順序和運(yùn)算法則，靈活運(yùn)用所學(xué)的運(yùn)算定律簡(jiǎn)便計(jì)算．