题目内容
(1)1.25×17.6+36÷0.8+2.64×12.5(2)9998+998+99+9+6
(3)
267+123×894 |
894×124-627 |
(4)75×4.67+17.9×2.5
(5)1991×199219921992-1992×199119911991
(6)
1 |
2 |
1 |
6 |
1 |
12 |
1 |
20 |
1 |
30 |
分析:(1)先把除法变成乘法,再运用乘法分配律简算;
(2)运用凑整法简算;
(3)先把分母中的123+1,再运用乘法分配律化简,最后约分即可;
(4)先根据积不变的规律,把两部分乘法都变成含有因数25的算式,再运用乘法分配律简算;
(5)两个重复算式都提取出1991×1992,再运用乘法分配律简算;
(6)
=1-
,
=
-
…由此进行化简求解.
(2)运用凑整法简算;
(3)先把分母中的123+1,再运用乘法分配律化简,最后约分即可;
(4)先根据积不变的规律,把两部分乘法都变成含有因数25的算式,再运用乘法分配律简算;
(5)两个重复算式都提取出1991×1992,再运用乘法分配律简算;
(6)
1 |
2 |
1 |
2 |
1 |
6 |
1 |
2 |
1 |
3 |
解答:解:(1)1.25×17.6+36÷0.8+2.64×12.5,
=1.25×17.6+36×1.25+26.4×1.25,
=1.25×(17.6+36+26.4),
=1.25×80,
=100;
(2)9998+998+99+9+6,
=(10000-2)+(1000-2)+(100-1)+(10-1)+6,
=(10000+1000+100+10)-(2+2+1+1-6),
=11110-0,
=11110;
(3)
,
=
,
=
,
=
,
=1;
(4)75×4.67+17.9×2.5
=(75÷3)×(4.67×3)+(17.9÷10)×(2.5×10),
=25×14.01+1.79×25,
=25×(14.01+1.79),
=25×15.8,
=395;
(5)1991×199219921992-1992×199119911991,
=1991×199219921992-1992×199119911991,
=1991×1992×100010001-1992×1991×100010001,
=1991×1992×(100010001-100010001),
=1991×1992×0,
=0;
(6)
+
+
+
+
,
=(1-
)+(
-
)+(
-
)+(
-
)+(
-
),
=1-
+
-
+
-
+
-
+
-
,
=1-
,
=
.
=1.25×17.6+36×1.25+26.4×1.25,
=1.25×(17.6+36+26.4),
=1.25×80,
=100;
(2)9998+998+99+9+6,
=(10000-2)+(1000-2)+(100-1)+(10-1)+6,
=(10000+1000+100+10)-(2+2+1+1-6),
=11110-0,
=11110;
(3)
267+123×894 |
894×124-627 |
=
267+123×894 |
894×(123+1)-627 |
=
267+123×894 |
894×123+894×1-627 |
=
267+123×894 |
894×123+267 |
=1;
(4)75×4.67+17.9×2.5
=(75÷3)×(4.67×3)+(17.9÷10)×(2.5×10),
=25×14.01+1.79×25,
=25×(14.01+1.79),
=25×15.8,
=395;
(5)1991×199219921992-1992×199119911991,
=1991×199219921992-1992×199119911991,
=1991×1992×100010001-1992×1991×100010001,
=1991×1992×(100010001-100010001),
=1991×1992×0,
=0;
(6)
1 |
2 |
1 |
6 |
1 |
12 |
1 |
20 |
1 |
30 |
=(1-
1 |
2 |
1 |
2 |
1 |
3 |
1 |
3 |
1 |
4 |
1 |
4 |
1 |
5 |
1 |
5 |
1 |
6 |
=1-
1 |
2 |
1 |
2 |
1 |
3 |
1 |
3 |
1 |
4 |
1 |
4 |
1 |
5 |
1 |
5 |
1 |
6 |
=1-
1 |
6 |
=
5 |
6 |
点评:简算时看到此类“几个乘法相加减”的题,先观察这几个乘法有没有相同因数,或者能不能转化出相同因数
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