题目内容
脱式计算,能简算的要简算
①
-(
-
)
②31.9×18-8×31.9
③
+
+
+
④
-
+
.
①
1 |
2 |
3 |
4 |
3 |
8 |
②31.9×18-8×31.9
③
13 |
14 |
13 |
15 |
1 |
14 |
2 |
15 |
④
3 |
4 |
1 |
28 |
3 |
14 |
分析:①先计算括号内部的,再计算括号外面的.②运用乘法的分配律进行计算即可③运用加法的结合律及交换律进行计算.④同级运算从左向右依次计算.
解答:解:①
-(
-
),
=
-(
-
),
=
-
,
=
;
②31.9×18-8×31.9,
=31.9×(18-8),
=319;
③
+
+
+
,
=(
+
)+(
+
),
=1+1,
=2;
④
-
+
,
=
-
+
,
=
,
=
;
1 |
2 |
3 |
4 |
3 |
8 |
=
1 |
2 |
6 |
8 |
3 |
8 |
=
4 |
8 |
3 |
8 |
=
1 |
8 |
②31.9×18-8×31.9,
=31.9×(18-8),
=319;
③
13 |
14 |
13 |
15 |
1 |
14 |
2 |
15 |
=(
13 |
14 |
1 |
14 |
13 |
15 |
2 |
15 |
=1+1,
=2;
④
3 |
4 |
1 |
28 |
3 |
14 |
=
21 |
28 |
1 |
28 |
6 |
28 |
=
26 |
28 |
=
13 |
14 |
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
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