Question

3．脱式计算，能简便的要用简便方法计算．

0.73×102	0.25×9.87×4	26×15.7+15.7×74
3.78×0.5-0.65	3.98+13.4×0.24	（9.37+9.37+9.37+9.37）×2.5
0.85×99	7.8×5.6+2.3×4.4	76.3×27-76.3×17

Answer 1

分析 ①⑦可用乘法分配律简算，
②运用乘法交换律简算，
③⑨逆用乘法分配律简算，
④先算乘法再算减法，
⑤先算乘法再算加法，
⑥先根据乘法的意义把9.37+9.37+9.37+9.37化为9.37×4，再运用乘法的结合律进行简算，
⑧先算乘法再算加法．

解答 解：①0.73×102
=0.73×（100+2）
=0.73×100+0.73×2
=73+1.46
=74.46 

②0.25×9.87×4
=0.25×4×9.87
=1×9.87
=9.87

③26×15.7+15.7×74
=15.7×（26+74）
=15.7×100
=1570

④3.78×0.5-0.65
=1.89-0.65
=1.24 

⑤3.98+13.4×0.24  
=3.98+3.216
=7.196        

⑥（9.37+9.37+9.37+9.37）×2.5  
=（9.37×4）×2.5
=9.37×（4×2.5）
=9.37×10
=93.7  

⑦0.85×99
=0.85×（100-1）
=0.85×100-0.85
=85-0.85
=84.15    

⑧7.8×5.6+2.3×4.4
=43.68+10.12
=53.8

⑨76.3×27-76.3×17
=76.3×（27-17）
=76.3×10
=763

点评 此题考查小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．