1-1/10+3-1/40+5-1/88+7-1/154+9-1/238+11-1/340

题目

1-1/10+3-1/40+5-1/88+7-1/154+9-1/238+11-1/340

答案

原式=1+3+5+7+9+11-（1/10+1/40+1/88+1/154+1/238+1/340)=36-(1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14+1/14-1/17+1/17-1/20)×1/3=36-(1/2-1/20)×1/3=36-9/20×1/3=36-3/20=35又17/20