
下面各题,怎样算简便就怎样算.(1)2005×20032004(2)(15+27)×5×7(3)99989+9989+989+13(4)25
下面各题,怎样算简便就怎样算.(1)2005×20032004(2)(15+27)×5×7(3)99989+9989+989+13(4)25×1.25×32....
下面各题,怎样算简便就怎样算.(1)2005×20032004(2)(15+27)×5×7(3)99989+9989+989+13(4)25×1.25×32.
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(1)2005×
=(2004+1)×
,
=2004×
+
,
=2003+
,
=2003
;
(2)(
+
)×5×7
=
×5×7+
×5×7,
=7+10,
=17;
(3)999
+99
+9
+
=1000-
+100-
+10-
+
,
=(1000+100+10)-(
×3-
),
=1110-(
-
),
=1110-0,
=1110;
(4)25×1.25×32.
=25×1.25×4×8,
=(25×4)×(1.25×8),
=100×10,
=1000.
2003 |
2004 |
=(2004+1)×
2003 |
2004 |
=2004×
2003 |
2004 |
2003 |
2004 |
=2003+
2003 |
2004 |
=2003
2003 |
2004 |
(2)(
1 |
5 |
2 |
7 |
=
1 |
5 |
2 |
7 |
=7+10,
=17;
(3)999
8 |
9 |
8 |
9 |
8 |
9 |
1 |
3 |
=1000-
1 |
9 |
1 |
9 |
1 |
9 |
1 |
3 |
=(1000+100+10)-(
1 |
9 |
1 |
3 |
=1110-(
1 |
3 |
1 |
3 |
=1110-0,
=1110;
(4)25×1.25×32.
=25×1.25×4×8,
=(25×4)×(1.25×8),
=100×10,
=1000.
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