计算:1/2+(1/3+2/3)+(3/4+2/4+1/4)+(4/5+3/5+2/5+1/5)+…+(19/20+18/20+…+1/20)=_.

问题描述:

计算:

1
2
+(
1
3
+
2
3
)+(
3
4
+
2
4
+
1
4
)+(
4
5
+
3
5
+
2
5
+
1
5
)+…+(
19
20
+
18
20
+…+
1
20
)=______.

1
2
+(
1
3
+
2
3
)+(
3
4
+
2
4
+
1
4
)+(
4
5
+
3
5
+
2
5
+
1
5
)+…+(
19
20
+
18
20
+…+
1
20
),
=
1
2
+1+1
1
2
+2+…+9
1
2

=
1
2
+
2
2
+
3
2
+…+
19
2

=(1+2+…+19)÷2,
=(1+19)×19÷2÷2,
=95.
故答案为:95.