问题 解答题
1
2
+
5
6
+
11
12
+
19
20
+
29
30
+…+
9701
9702
+
9899
9900
答案

1
2
+
5
6
+
11
12
+
19
20
+
29
30
+…+
9701
9702
+
9899
9900

=(1-

1
2
)+(1-
1
6
)+(1-
1
12
)+…+(1-
1
9900

=1×99-(

1
2
+
1
6
+
1
12
+…+
1
9900
),

=99-(

1
1×2
+
1
2×3
+
1
3×4
…+
1
99×100
),

=99-(1-

1
2
+
1
2
-
1
3
+
1
3
-
1
4
+…+
1
99
-
1
100
),

=99-(1-

1
100
),

=99-

99
100

=98

1
100

单项选择题
单项选择题