题目内容

17.用简便方法计算
101×37            125×0.5×8                25×72
280÷35            4.87+13.9-1.87+6.1         54.82-5.31-14.69
67000÷8÷125      24×89-24×64              76×20-20

分析 (1)(7)(9)根据乘法分配律简算即可.
(2)运用乘法交换律与结合律简算;
(3)把72看做4×18,运用乘法结合律简算;
(4)把37看做7×5,运用除法的运算性质简算;
(5)运用加法交换律与结合律简算;
(6)运用减法的性质简算;
(7)运用除法的运算性质简算.

解答 解:(1)101×37
=(100+1)×37
=100×37+37
=3737

(2)125×0.5×8  
=(125×8)×0.5 
=1000×0.5
=500

(3)25×72
=(25×4)×18
=100×18
=1800

(4)280÷35            
=280÷(7×5)
=280÷7÷5
=40÷5
=8

(5)4.87+13.9-1.87+6.1 
=(4.87-1.87)+(13.9+6.1)
=3+20
=23

(6)54.82-5.31-14.69
=54.82-(5.31+14.69)
=54.82-20
=34.82

(7)67000÷8÷125      
=67000÷(8×125)
=67000÷1000
=67

(8)24×89-24×64              
=24×(89-64)
=24×25
=6×(4×25)
=6×100
=600

(9)76×20-20
=(76-1)×20
=75×20
=1500

点评 完成本题要注意分析式中数据,运用合适的简便方法计算.

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