题目内容
用你喜欢的方法计算.
①
+
+
②
-(
+
)
③2-
-
④
+
+
-
.
①
| 3 |
| 5 |
| 7 |
| 10 |
| 2 |
| 5 |
②
| 7 |
| 8 |
| 3 |
| 8 |
| 2 |
| 5 |
③2-
| 15 |
| 19 |
| 4 |
| 19 |
④
| 6 |
| 11 |
| 11 |
| 15 |
| 5 |
| 11 |
| 6 |
| 15 |
分析:①运用加法交换律简算;
②根据减去两个数的和,等于连续减去这两个数简算;
③根据连续减去两个数,等于减去这两个数的和简算;
④运用加法结合律简算.
②根据减去两个数的和,等于连续减去这两个数简算;
③根据连续减去两个数,等于减去这两个数的和简算;
④运用加法结合律简算.
解答:解:①
+
+
,
=(
+
)+
,
=1+
,
=1
;
②
-(
+
),
=
-
-
,
=
-
,
=
;
③2-
-
,
=2-(
+
),
=2-1,
=1;
④
+
+
-
,
=(
+
)+(
-
),
=1+
=1
.
| 3 |
| 5 |
| 7 |
| 10 |
| 2 |
| 5 |
=(
| 3 |
| 5 |
| 2 |
| 5 |
| 7 |
| 10 |
=1+
| 7 |
| 10 |
=1
| 7 |
| 10 |
②
| 7 |
| 8 |
| 3 |
| 8 |
| 2 |
| 5 |
=
| 7 |
| 8 |
| 3 |
| 8 |
| 2 |
| 5 |
=
| 1 |
| 2 |
| 2 |
| 5 |
=
| 1 |
| 10 |
③2-
| 15 |
| 19 |
| 4 |
| 19 |
=2-(
| 15 |
| 19 |
| 4 |
| 19 |
=2-1,
=1;
④
| 6 |
| 11 |
| 11 |
| 15 |
| 5 |
| 11 |
| 6 |
| 15 |
=(
| 6 |
| 11 |
| 5 |
| 11 |
| 11 |
| 15 |
| 6 |
| 15 |
=1+
| 1 |
| 3 |
=1
| 1 |
| 3 |
点评:本题考查了加减法中常用的简算方法,完成本题要注意分析式中数据,运用合适的简便方法计算.
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