试题:
用简便方法计算,并要写出主要的简算过程.
7
11
+
1
5
+
4
11
+
3
5

②12.5×8×4×0.25
③5-
9
4
÷
45
8
-
3
5

④4.9×6.4+14×0.36-6.4×3.5.

答案:

我来补答
7
11
+
1
5
+
4
11
+
3
5

=(
7
11
+
4
11
)+(
1
5
+
3
5
),
=1+
4
5

=1
4
5


②12.5×8×4×0.25,
=(12.5×8)×(4×0.25),
=100×1,
=100;

③5-
9
4
÷
45
8
-
3
5

=5-
9
4
×
8
45
-
3
5

=5-
2
5
-
3
5

=5-(
2
5
+
3
5
),
=5-1,
=4;
④4.9×6.4+14×0.36-6.4×3.5,
=(4.9-3.5)×6.4+14×0.36,
=1.4×6.4+1.4×3.6,
=1.4×(6.4+3.6),
=1.4×10,
=14.
 
 
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