题目内容

用简便方法计算(写出主要过程)
42
5
+6.85+1.6+
43
20
51
4
÷
6
5
+5.25×
5
6
3.5%×9.9.
(1)
42
5
+6.85+1.6+
43
20

=8.4+6.85+1.6+2.15,
=(8.4+1.6)+(6.85+2.15),
=10+9,
=19;

(2)
51
4
÷
6
5
+5.25×
5
6

=12.75×
5
6
+5.25×
5
6

=(12.75+5.25)×
5
6

=18×
5
6

=15;

(3)3.5%×9.9,
=3.5%×(10-0.1),
=3.5%×10-3.5%×0.1,
=0.35-0.0035,
=0.3465.
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