分析:(1)把6
变成6.6,642.9×66变成6429×6.6,3÷
变成3×6.6,然后利用乘法的分配律计算简便;
(2)把分母382×498-116变成(381+1)×498-116=381×498+498-116=381×498+(498-116)=498×381+382,然后计算简便;
(3)把原算式变成(1+3+5+7+9+11)+(
+
+
+
+
)利用加法的结合律计算简便;
(4)根据等式的性质,方程的两边同时减去
x得出
x-
=-
,再根据等式的性质,方程的两边同时加上
,得出
x=
,两边同除以
即可.
3 |
5 |
5 |
33 |
(2)把分母382×498-116变成(381+1)×498-116=381×498+498-116=381×498+(498-116)=498×381+382,然后计算简便;
(3)把原算式变成(1+3+5+7+9+11)+(
1 |
6 |
1 |
12 |
1 |
20 |
1 |
30 |
1 |
42 |
(4)根据等式的性质,方程的两边同时减去
1 |
2 |
1 |
6 |
3 |
4 |
1 |
3 |
3 |
4 |
1 |
6 |
5 |
12 |
1 |
6 |
解答:解;(1)6
×3574+642.9×66-3÷
,
=6.6×3574+6429×6.6-3×6.6,
=6.6×(3574+6429-3),
=6.6×10000,
=66000;
(2)
,
=(498×381+382)÷[(381+1)×498-116],
=(498×381+382)÷[381×498+498-116],
=(498×381+382)÷[381×498+(498-116)],
=(498×381+382)÷(381×498+382),
=1;
(3)1+3
+5
+7
+9
+11
,
=(1+3+5+7+9+11)+(
+
+
+
+
),
=36+
,
=36
;
(4)
x-
=
x-
,
x-
-
x=
x-
-
x,
x-
=-
,
x-
+
=-
+
,
x=
,
x÷
=
÷
,
x=
.
3 |
5 |
5 |
33 |
=6.6×3574+6429×6.6-3×6.6,
=6.6×(3574+6429-3),
=6.6×10000,
=66000;
(2)
498×381+382 |
382×498-116 |
=(498×381+382)÷[(381+1)×498-116],
=(498×381+382)÷[381×498+498-116],
=(498×381+382)÷[381×498+(498-116)],
=(498×381+382)÷(381×498+382),
=1;
(3)1+3
1 |
6 |
1 |
12 |
1 |
20 |
1 |
30 |
1 |
42 |
=(1+3+5+7+9+11)+(
1 |
6 |
1 |
12 |
1 |
20 |
1 |
30 |
1 |
42 |
=36+
5 |
14 |
=36
5 |
14 |
(4)
2 |
3 |
3 |
4 |
1 |
2 |
1 |
3 |
2 |
3 |
3 |
4 |
1 |
2 |
1 |
2 |
1 |
3 |
1 |
2 |
1 |
6 |
3 |
4 |
1 |
3 |
1 |
6 |
3 |
4 |
3 |
4 |
1 |
3 |
3 |
4 |
1 |
6 |
5 |
12 |
1 |
6 |
1 |
6 |
5 |
12 |
1 |
6 |
x=
5 |
2 |
点评:此题考查四则混合运算和应用运算定律进行简便计算,注意运算顺序和运算法则,根据算式的特点灵活利用运算定律简便计算,解方程根据等式的基本性质,注意等号对齐.