问题 解答题
用简便方法计算.
24×
2
7
×
5
72
×21
17×
11
23
+17÷
23
12
3
5
×
2
3
+
2
5
÷1
1
2
3
85
×86.
答案

(1)24×

2
7
×
5
72
×21

=(24×

5
72
)×(
2
7
×21)

=

5
3
×6

=10;

(2)17×

11
23
+17÷
23
12

=17×

11
23
+17×
12
23

=17×(

11
23
+
12
23

=17×1

=17;

(3)

3
5
×
2
3
+
2
5
÷1
1
2

=

3
5
×
2
3
+
2
5
×
2
3

=(

3
5
+
2
5
)×
2
3

=1×

2
3

=

2
3

(4)

3
85
×86

=

3
85
×(85+1)

=

3
85
×85+
3
85

=3+

3
85

=3

3
85

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