题目内容
计算下面各题,怎样简便就怎样计算. 420÷216÷18×17 |
25×12.5×32 | ||||||||||||||
|
40÷[
|
分析:(1)按照从左到右的顺序计算;
(2)先把32分解成8×4,再运用乘法结合律简算;
(3)先把除法变成乘法,再运用乘法分配律简算;
(4)先算小括号里面的加法,再算中括号里面的乘法,最后算括号外的除法.
(2)先把32分解成8×4,再运用乘法结合律简算;
(3)先把除法变成乘法,再运用乘法分配律简算;
(4)先算小括号里面的加法,再算中括号里面的乘法,最后算括号外的除法.
解答:解:(1)420÷216÷18×17,
=
÷18×17,
=
×17,
=
;
(2)25×12.5×32,
=25×12.5×8×4,
=(25×4)×(12.5×8),
=100×100,
=10000;
(3)
×
+
÷
,
=
×
+
×
,
=(
+
)×
,
=1×
,
=
;
(4)40÷[
×(
+
)],
=40÷[
×
],
=40÷
,
=80.
=
35 |
18 |
=
35 |
324 |
=
595 |
324 |
(2)25×12.5×32,
=25×12.5×8×4,
=(25×4)×(12.5×8),
=100×100,
=10000;
(3)
1 |
6 |
5 |
12 |
5 |
12 |
6 |
5 |
=
1 |
6 |
5 |
12 |
5 |
12 |
5 |
6 |
=(
1 |
6 |
5 |
6 |
5 |
12 |
=1×
5 |
12 |
=
5 |
12 |
(4)40÷[
4 |
7 |
3 |
8 |
1 |
2 |
=40÷[
4 |
7 |
7 |
8 |
=40÷
1 |
2 |
=80.
点评:此题是考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算.
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