91=7*13
分母为91的所有最简真分数共有91-(91/7)-(91/13)+(91/91)=91-13-7+1=72(个)
分母为91的所有最简真分数的和等于
((1+2+3+……+91)- (7+14+21+……+91)- (13+26+39+……+91)+91)/91
=(4186-637-364+91)/91
=3276/91
=36
91=7*13
分母为91的所有最简真分数共有91-(91/7)-(91/13)+(91/91)=91-13-7+1=72(个)
分母为91的所有最简真分数的和等于
((1+2+3+……+91)- (7+14+21+……+91)- (13+26+39+……+91)+91)/91
=(4186-637-364+91)/91
=3276/91
=36