试题:
用简便方法计算.
23-
12
17
-
5
17

3
4
+
2
5
)×20
0.4×1.25×25×8.

答案:

我来补答
(1)23-
12
17
-
5
17

=23-(
12
17
+
5
17
),
=23-1,
=22;

(2)(
3
4
+
2
5
)×20,
=
3
4
×20+
2
5
×20,
=15+8,
=23;

(3)0.4×1.25×25×8,
=(0.4×25)×(1.25×8),
=10×10,
=100.
 
 
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