题目内容
简便计算. 17×25×40 | 36×250 | 72×37+28×37 |
99×65 | 125×25×8 | 125×79+125 |
78×101 | (80+8)×125 | 24×117-17×24. |
解:(1)17×25×40,
=17×(25×40),
=17×1000,
=17000;
(2)36×250,
=9×(4×250),
=9×1000,
=9000;
(3)72×37+28×37,
=(72+28)×37,
=100×37,
=3700;
(4)99×65,
=(100-1)×65,
=6500-65,
=6435;
(5)125×25×8,
=(125×8)×25,
=1000×25,
=25000;
(6)125×79+125,
=125×(79+1),
=125×80,
=10000;
(7)78×101,
=78×(100+1),
=7800+78,
=7878;
(8)(80+8)×125,
=80×125+8×125,
=10000+1000,
=11000;
(9)24×117-17×24,
=24×(117-17),
=24×100,
=2400.
分析:(1)运用乘法结合律简算;
(2)把36看作9×4,运用乘法结合律简算;
(3)(6)(8)(9)运用乘法分配律简算;
(4)把99看作100-1,运用乘法结合律简算;
(5)运用乘法交换律与结合律简算;
(7)把101看作100+1,运用乘法分配律简算.
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.
=17×(25×40),
=17×1000,
=17000;
(2)36×250,
=9×(4×250),
=9×1000,
=9000;
(3)72×37+28×37,
=(72+28)×37,
=100×37,
=3700;
(4)99×65,
=(100-1)×65,
=6500-65,
=6435;
(5)125×25×8,
=(125×8)×25,
=1000×25,
=25000;
(6)125×79+125,
=125×(79+1),
=125×80,
=10000;
(7)78×101,
=78×(100+1),
=7800+78,
=7878;
(8)(80+8)×125,
=80×125+8×125,
=10000+1000,
=11000;
(9)24×117-17×24,
=24×(117-17),
=24×100,
=2400.
分析:(1)运用乘法结合律简算;
(2)把36看作9×4,运用乘法结合律简算;
(3)(6)(8)(9)运用乘法分配律简算;
(4)把99看作100-1,运用乘法结合律简算;
(5)运用乘法交换律与结合律简算;
(7)把101看作100+1,运用乘法分配律简算.
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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