分析:(1)把6
變成6.6,642.9×66變成6429×6.6,3÷
變成3×6.6,然后利用乘法的分配律計(jì)算簡(jiǎn)便;
(2)把分母382×498-116變成(381+1)×498-116=381×498+498-116=381×498+(498-116)=498×381+382,然后計(jì)算簡(jiǎn)便;
(3)把原算式變成(1+3+5+7+9+11)+(
+
+
+
+
)利用加法的結(jié)合律計(jì)算簡(jiǎn)便;
(4)根據(jù)等式的性質(zhì),方程的兩邊同時(shí)減去
x得出
x-
=-
,再根據(jù)等式的性質(zhì),方程的兩邊同時(shí)加上
,得出
x=
,兩邊同除以
即可.
3 |
5 |
5 |
33 |
(2)把分母382×498-116變成(381+1)×498-116=381×498+498-116=381×498+(498-116)=498×381+382,然后計(jì)算簡(jiǎn)便;
(3)把原算式變成(1+3+5+7+9+11)+(
1 |
6 |
1 |
12 |
1 |
20 |
1 |
30 |
1 |
42 |
(4)根據(jù)等式的性質(zhì),方程的兩邊同時(shí)減去
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 |
點(diǎn)評(píng):此題考查四則混合運(yùn)算和應(yīng)用運(yùn)算定律進(jìn)行簡(jiǎn)便計(jì)算,注意運(yùn)算順序和運(yùn)算法則,根據(jù)算式的特點(diǎn)靈活利用運(yùn)算定律簡(jiǎn)便計(jì)算,解方程根據(jù)等式的基本性質(zhì),注意等號(hào)對(duì)齊.