The summation formula of proportional sequence is [a1(1-q n)]/(1-q), then when q

& lt 1 and n->; At infinity, the limit of this formula is a 1/( 1-q). Because the cyclic decimal 0.a cycles ... = a/10+a/100+a/1000+a/10000 ..., each addend of it just constitutes an infinite geometric series, q = 65438+. At this time, a 1=0.9, q =110, and it is easy to get 0.9 cycles ... = 0.9/(1-10) =/kloc-0.