3+13/6+37/12+81/20+151/30+253/42+393/56+577/72+811/90
=3+2+1/6+3+1/12+4+1/20+5+1/30+6+1/42+7+1/56+8+1/72+9+1/90
=3+2+3+4+5+6+7+8+9+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90
=3+(2+9)*8/2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8+1/8*9+1/9*10
=3+44+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10
=47+1/2-1/10
=47+5/10-1/10
=47+2/5
=47又2/5