题目内容
计算下列各题.(能简算的要简算) 7÷
|
15÷
| ||||||||||||||
|
3-
| ||||||||||||||
|
|
分析:②可以按照乘法分配律简算,⑥可以用乘法结合律简算,其它题目先算乘除,再算加减,有括号的先算括号里面的.
解答:解:①7÷
-
÷7,
=7×
-
×
,
=9-
,
=8
;
②15÷
+15×
,
=15×
+15×
,
=(
+
)×15,
=2×15,
=30;
③
÷[
÷(
-
)],
=
÷[
÷
],
=
÷
,
=
;
④3-
×
-
,
=3-
-
,
=3-(
+
),
=3-1,
=2;
⑤
÷[
×(
+
)],
=
÷[
×
],
=
×6,
=
;
⑥
×(7×26),
=
×26×7,
=1×7,
=7.
7 |
9 |
7 |
9 |
=7×
9 |
7 |
7 |
9 |
1 |
7 |
=9-
1 |
9 |
=8
8 |
9 |
②15÷
8 |
9 |
7 |
8 |
=15×
9 |
8 |
7 |
8 |
=(
9 |
8 |
7 |
8 |
=2×15,
=30;
③
3 |
22 |
5 |
4 |
14 |
3 |
1 |
2 |
=
3 |
22 |
5 |
4 |
25 |
6 |
=
3 |
22 |
3 |
10 |
=
5 |
11 |
④3-
5 |
18 |
27 |
40 |
13 |
16 |
=3-
3 |
16 |
13 |
16 |
=3-(
3 |
16 |
13 |
16 |
=3-1,
=2;
⑤
8 |
15 |
5 |
32 |
9 |
10 |
1 |
6 |
=
8 |
15 |
5 |
32 |
32 |
30 |
=
8 |
15 |
=
16 |
5 |
⑥
1 |
26 |
=
1 |
26 |
=1×7,
=7.
点评:运算定律是常用的简算方法,要灵活运用.
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