问题
解答题
求下面所有分数的和:
|
答案
+1 1
+1 2
+2 2
+1 2
+1 3
+2 3
+3 3
+2 3
+…+1 3
+…+1 1991
+…+1991 1991 1 1991
=
+(1 1
+1 2
+2 2
)+(1 2
+1 3
+2 3
+3 3
+2 3
)+…+(1 3
+…+1 1991
+…1991 1991
),1 1991
=1+2+3+…+1991,
=(1+1991)×1991÷2,
=1983036.