6/1*7 - 6/7*13 - 6/13*19 - 6/19*25-…-6/97*103

题目

6/1*7 - 6/7*13 - 6/13*19 - 6/19*25-…-6/97*103
A．433/567 B．532/653 C．522/721 D． 436/673

答案

C
6/1*7-6/7*13-6/13*19-6/19*25-…-6/97*103
=(1-1/7)-(1/7-1/13)-(1/13-1/19)-(1/19-1/25)…-(1/97-1/103)
=1-1/7-1/7+1/13-1/13+1/19-1/19+1/25…-1/97+1/103
=1-2/7+1/103
=721/721-206/721+7/721
=522/721