问题 解答题
简便运算:
(1)2.9+29.9+299.9+2999.9
(2)(
5
9
+
7
18
1
18
×5
答案

(1)2.9+29.9+299.9+2999.9,

=3-0.1+30-0.1+300-0.1+3000-0.1,

=3+30+300+3000-(0.1+0.1+0.1+0.1),

=3333-0.4,

=3332.6;

(2)(

5
9
+
7
18
1
18
×5,

=(

5
9
+
7
18
)×18×5,

=

5
9
×18×5+
7
18
×18×5,

=50-35,

=15.

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