题目内容
能简算的要简算. 5×999+5+99×7+7+3×9+3+9 |
999×778+333×666 |
15.6×13.1-15.6-15.6×2.1 | [20-(90.75÷6.6+2.25)]×11.6. |
分析:(1)把这个算式结合成3部分,分别运用乘法分配律简算;
(2)先运用积不变规律,把333×666边长999×222,再运用乘法分配律简算;
(3)运用乘法分配律简算;
(4)先算小括号里面的除法,再算小括号里面的加法,然后算中括号里面的减法,最后算括号外的乘法.
(2)先运用积不变规律,把333×666边长999×222,再运用乘法分配律简算;
(3)运用乘法分配律简算;
(4)先算小括号里面的除法,再算小括号里面的加法,然后算中括号里面的减法,最后算括号外的乘法.
解答:解:(1)5×999+5+99×7+7+3×9+3+9,
=5×(999+1)+7×(99+1)+3×(9+1)+9,
=5×1000+7×100+3×10+9,
=5000+700+30+9,
=5700+30+9,
=5739;
(2)999×778+333×666,
=999×778+999×222,
=999×(778+222),
=999×1000,
=999000;
(3)15.6×13.1-15.6-15.6×2.1,
=15.6×(13.1-1-2.1),
=15.6×10,
=156;
(4)[20-(90.75÷6.6+2.25)]×11.6,
=[20-(13.75+2.25)]×11.6,
=[20-16]×11.6,
=4×11.6,
=46.4.
=5×(999+1)+7×(99+1)+3×(9+1)+9,
=5×1000+7×100+3×10+9,
=5000+700+30+9,
=5700+30+9,
=5739;
(2)999×778+333×666,
=999×778+999×222,
=999×(778+222),
=999×1000,
=999000;
(3)15.6×13.1-15.6-15.6×2.1,
=15.6×(13.1-1-2.1),
=15.6×10,
=156;
(4)[20-(90.75÷6.6+2.25)]×11.6,
=[20-(13.75+2.25)]×11.6,
=[20-16]×11.6,
=4×11.6,
=46.4.
点评:乘法分配律是常用的简便运算的方法,要熟练掌握,灵活运用.

练习册系列答案
相关题目