42/1+1/56+1/72+1/90+1/110快啊.

42/1+1/56+1/72+1/90+1/110快啊.
42/1+1/56+1/72+1/90+1/110
快啊.

42/1+1/56+1/72+1/90+1/110快啊.
1/(m*n)(m=6.7.8...,n=7.8.9.)

3238/77

因为1/42=1/(6*7)=1/6-1/7
所以原式=1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11=5/66

(1 / 42) + (1 / 56) + (1 / 72) + (1 / 90) + (1 / 110) = 0.0757575758