题目内容
脱式计算 168.1÷(4.3×2-0.4) |
12×(
| ||||||
7.8÷[32×(1-
|
31.9×8-0.8×319. |
分析:①③根据四则混合运算的运算顺序计算即可:先算乘除,再算加减,有括号的要先算括号里面的;
②可根据乘法分配律计算;
④可根据乘法的性质及乘法分配律计算.
②可根据乘法分配律计算;
④可根据乘法的性质及乘法分配律计算.
解答:解:①168.1÷(4.3×2-0.4)
=168.1÷(8.6-0.4),
=168.1÷8.2,
=20.5;
②12×(
+
-
)
=12×
+12×
-12×
,
=3+2-4,
=1;
③7.8÷[32×(1-
)+3.6]
=7.8÷[32×
+3.6],
=7.8÷[12+3.6],
=7.8÷15.6,
=0.5;
④31.9×8-0.8×319
=31.9×8-8×31.9,
=(8-8)×31.9,
=0×31.9,
=0.
=168.1÷(8.6-0.4),
=168.1÷8.2,
=20.5;
②12×(
1 |
4 |
1 |
6 |
1 |
3 |
=12×
1 |
4 |
1 |
6 |
1 |
3 |
=3+2-4,
=1;
③7.8÷[32×(1-
5 |
8 |
=7.8÷[32×
3 |
8 |
=7.8÷[12+3.6],
=7.8÷15.6,
=0.5;
④31.9×8-0.8×319
=31.9×8-8×31.9,
=(8-8)×31.9,
=0×31.9,
=0.
点评:当算式中同时含有中括号与小括号时,要先算中括号里面的,再算小括号里面的.
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