Question

2分之1加6分之1加12分之1加20分之1加30分之1等于?简便

Answer 1

1/2+1/6+1/12+1/20+1/30
=1/2+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)
=1/2-1/6
=2/6
=1/3