(9又2分之1+7又6分之1+5又12分之1+3又20分之1+1又30分之1)×12
=【(9+7+5+3+1)+(1/2+1/6+1/12+1/20+1/30)】×12
=【25+(1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6)】×12
=【25+1-1/6】×12
=【25+5/6】×12
=25×12+5/6×12
=300+10
=310
(9又2分之1+7又6分之1+5又12分之1+3又20分之1+1又30分之1)×12
=【(9+7+5+3+1)+(1/2+1/6+1/12+1/20+1/30)】×12
=【25+(1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6)】×12
=【25+1-1/6】×12
=【25+5/6】×12
=25×12+5/6×12
=300+10
=310