问题 解答题
(
5
6
+
7
12
+
2
3
)
×48
18
3
5
×
19
20
+2
2
5
×
19
20
-
19
20

41
1
3
×
3
4
+51
1
4
×
4
5
+61
1
5
×
5
6

2001×
1999
2000

1998÷1998
1998
1999

1
2
+
1
6
+
1
12
+
1
20
+
1
30
+
1
42
+
1
56
答案

(1))(

5
6
+
7
12
+
2
3
)×48

=

5
6
×48+
7
12
×48+
2
3
×48,

=40+28+32,

=100;

(2)18

3
5
×
19
20
+2
2
5
×
19
20
-
19
20

=(18

3
5
+2
2
5
-1)×
19
20

=20×

19
20

=19;

(3)41

1
3
×
3
4
+51
1
4
×
4
5
+61
1
5
×
5
6

=(40+1

1
3
)×
3
4
+(50+1
1
4
)×
4
5
+(60+1
1
5
)×
5
6

=40×

3
4
+
4
3
×
3
4
+50×
4
5
+
5
4
×
4
5
+60×
5
6
+
6
5
×
5
6

=30+1+40+1+50+1,

=123;

(4)2001×

1999
2000

=(2000+1)×

1999
2000

=2000×

1999
2000
+1×
1999
2000

=1999+

1999
2000

=1999

1999
2000

(5)1998÷1998

1998
1999

=19998÷

1999×1998+1998
1999

=1998×

1999
(1999+1)×1998

=

1999
2000

(6)

1
2
+
1
6
+
1
12
+
1
20
+
1
30
+
1
42
+
1
56

=

1
1×2
+
1
2×3
+
1
3×4
+
2
4×5
+
1
5×6
+
1
6×7
+
1
7×8

=1-

1
2
+
1
2
-
1
3
+
1
3
-
1
4
+…+
1
7
-
1
8

=

7
8

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