3分之1加6分之1加10分之1加15分之1加21分之一加28分之1加36分之1+45分之1 用简便方法计算

1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45
=(1/3+1/6)+(1/10+1/15)+(1/21+1/28)+(1/36+1/45)
=(2+1)/6+(3+2)/30+(4+3)/84+(5+4)/180
=1/2+1/6+1/12+1/20
=1/2+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)
=1-1/5
=4/5