题目内容
下面各题,怎样算简便就怎样算: (1)12×(
| (2)48×
| ||||||||
(3)3.7×
| (4)9.9+99.9+999.9. |
(1)12×(
+
-
)
=12×
+12×
-12×
,
=2+3-4,
=1;
(2)48×
,
=(49-1)×
,
=49×
-1×
,
=1-
,
=
;
(3)3.7×
+5.3×0.75+
,
=3.7×0.75+5.3×0.75+0.75,
=0.75×(3.7+5.3+1),
=0.75×10,
=7.5;
(4)9.9+99.9+999.9,
=(10-0.1)+(100-0.1)+(1000-0.1),
=(10+100+1000)-(0.1+0.1+0.1),
=1110-0.3,
=1109.7.
1 |
6 |
1 |
4 |
1 |
3 |
=12×
1 |
6 |
1 |
4 |
1 |
3 |
=2+3-4,
=1;
(2)48×
1 |
49 |
=(49-1)×
1 |
49 |
=49×
1 |
49 |
1 |
49 |
=1-
1 |
49 |
=
48 |
49 |
(3)3.7×
3 |
4 |
3 |
4 |
=3.7×0.75+5.3×0.75+0.75,
=0.75×(3.7+5.3+1),
=0.75×10,
=7.5;
(4)9.9+99.9+999.9,
=(10-0.1)+(100-0.1)+(1000-0.1),
=(10+100+1000)-(0.1+0.1+0.1),
=1110-0.3,
=1109.7.
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