脱式计算下面各题. ①24×2425

问题描述:

脱式计算下面各题.
①24×
24
25
1个回答 分类:数学 2014-09-19

问题解答:

我来补答
(1)24×
24
25,
=(25-1)×
24
25,
=25×
24
25-1×
24
25,
=24-
24
25,
=23
1
25;
(2)1994
1
2×79+
6
25×790+31×7.9,
=1994.5×79+2.4×79+3.1×79,
=(1994.5+2.4+3.1)×79,
=2000×79,
=158000;
(3)(
1
3-
1
2+1)×6,
=
1
3×6-
1
2×6+1×6,
=2-3+6,
=5;
(4)2007-2004+2001-1998+…+9-6+3,
=2007-2004+2001-1998+…+9-6+3-0,
=3×[(2007÷3-1)÷2+1],
=3×[(669-1)÷2+1],
=1005;
 
 
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