脱式计算(能简算的要简算)(1)(13+14-124)×24(2)(1+12)×(1-12)×(1+13)×(1-13)×…×(1+19)×(1-19)(3)2007×20052006(4)2.5×0.875+0.25×1.25.-数学

题文

脱式计算(能简算的要简算)
(1)(
1
3
+
1
4
-
1
24
)×24
(2)(1+
1
2
)×(1-
1
2
)×(1+
1
3
)×(1-
1
3
)×…×(1+
1
9
)×(1-
1
9

(3)2007×
2005
2006

(4)2.5×0.875+0.25×1.25.
题型:解答题  难度:中档

答案

(1)(
1
3
+
1
4
-
1
24
)×24,
=
1
3
×24+
1
4
×24-
1
24
×24,
=8+6-1,
=13;

(2)(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