题目内容

能简算的要简算
11
17
×51
(
4
7
-
1
3
)×21
5
9
×5×27
15
32
×
14
25
5
11
×
1
7
×14
3
5
-
3
5
×
1
2
19
25
×
1
5
+
19
25
×
4
5
7
8
×(
3
4
-
2
3
)
分析:(1)(3)(4)(5)直接约分计算即可;
(2)(7)利用乘法分配律简算;
(6)先算乘法,再算减法;
(8)先算减法,再算乘法.
解答:解:(1)
11
17
×51=33;

(2)(
4
7
-
1
3
)×21
=
4
7
×21-
1
3
×21
=12-7
=5;

(3)
5
9
×5×27
=
5
9
×27×5
=15×5
=75;

(4)
15
32
×
14
25
=
21
80


(5)
5
11
×
1
7
×14
=
5
11
×(
1
7
×14)
=
5
11
×2
=
10
11


(6)
3
5
-
3
5
×
1
2

=
3
5
-
3
10

=
3
10


(7)
19
25
×
1
5
+
19
25
×
4
5

=(
1
5
+
4
5
)×
19
25

=1×
19
25

=
19
25


(8)
7
8
×(
3
4
-
2
3

=
7
8
×
1
12

=
7
96
点评:此题考查分数四则混合运算,抓住运算顺序,掌握数字特点,适当选择运算定律简算.
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