1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8+1/8*9+1/9*10+.+1/96*97+1/97*98
=1－½＋½－1／3＋1／3－¼＋¼－1／5＋···＋1／97－1／98
=1－1／98
=97／98