题目内容

简便运算
(1)
3
5
×18-7×
3
5
-
3
5
(2)99×
97
98
(3)9.99×22.2+33.3×3.34 (4)
1
3
+
1
15
+
1
35
+
1
63
+
1
99
+
1
143
(1)
3
5
×18-7×
3
5
-
3
5

=
3
5
×(18-7-1),
=
3
5
×
10,
=6;

(2)99×
97
98

=(98+1)×
97
98

=98×
97
98
+
97
98

=97+
97
98

=97
97
98


(3)9.99×22.2+33.3×3.34,
=19.98×11.1+11.1×10.02,
=(19.98+10.02)×11.1,
=30×11.1,
=333;

(4)
1
3
+
1
15
+
1
35
+
1
63
+
1
99
+
1
143

=[(1-
1
3
)+(
1
3
-
1
5
)+(
1
5
-
1
7
)+(
1
7
-
1
9
)+(
1
9
-
1
11
)+(
1
11
-
1
13
)]×
1
2

=[1-
1
13
1
2

=
12
13
×
1
2

=
6
13
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