题目内容
脱式计算.(能简算的要简算)
×
+
×
(
+
)×88
×
×
×
×15×21.
2 |
5 |
1 |
4 |
1 |
4 |
3 |
5 |
(
5 |
11 |
7 |
44 |
5 |
8 |
12 |
31 |
8 |
5 |
4 |
5 |
6 |
7 |
考点:分数的四则混合运算
专题:运算顺序及法则
分析:(1)(2)运用乘法分配律简算.
(3)(4)运用乘法交换律与结合律简算.
(3)(4)运用乘法交换律与结合律简算.
解答:
解:(1)
×
+
×
=(
+
)×
=1×
=
;
(2)(
+
)×88
=
×88+
×88
=40+14
=54;
(3)
×
×
=(
×
)×
=1×
=
;
(4)
×
×15×21
=(
×15)×(
×21)
=12×18
=216.
2 |
5 |
1 |
4 |
1 |
4 |
3 |
5 |
=(
2 |
5 |
3 |
5 |
1 |
4 |
=1×
1 |
4 |
=
1 |
4 |
(2)(
5 |
11 |
7 |
44 |
=
5 |
11 |
7 |
44 |
=40+14
=54;
(3)
5 |
8 |
12 |
31 |
8 |
5 |
=(
5 |
8 |
8 |
5 |
12 |
31 |
=1×
12 |
31 |
=
12 |
31 |
(4)
4 |
5 |
6 |
7 |
=(
4 |
5 |
6 |
7 |
=12×18
=216.
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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