题目内容

简便计算
(1)(
1
15
-
1
51
)×17×5
(2)
1
5
×27+41÷
5
3

(3)(1+
1
2
)×(1-
1
2
)×(1+
1
3
)×(1-
1
3
)×…×(1+
1
9
)×(1-
1
9
(1)(
1
15
-
1
51
)×17×5,
=
1
15
×17×5-
1
51
×17×5,
=
17
3
-
5
3

=4;

(2)
1
5
×27+41÷
5
3

=
1
5
×27+41×
3
5

=
3
5
×9+41×
3
5

=
3
5
×(9+41),
=
3
5
×50,
=30;

(3)(1+
1
2
)×(1-
1
2
)×(1+
1
3
)×(1-
1
3
)×…×(1+
1
9
)×(1-
1
9
),
=
3
2
×
1
2
×
4
3
×
2
3
×…×
10
9
×
8
9

=
1
2
×(
3
2
×
2
3
)×(
4
3
×
3
4
)×…×(
9
8
×
8
9
)×
10
9

=
1
2
×
10
9

=
5
9
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