1/(2*7)+1/(7*12)+1/(12*17)+.1/(97*102)
=(1/5)*(1/2-1/7+1/7-1/12+1/12-1/17+.+1/97-1/102)
=(1/5)*(1/2-1/102)
=(1/5)*50/102
=10/102
=5/51