3分之1+6分之1+10分之1+15分之一+21分之一+28分之一=?简便怎么算?

1/3+1/6+1/10+1/15+1/21+1/28
=5/15+1/15+1/6+1/10+1/21+1/28
=(5+1)/15+1/6+1/10+1/21+1/28
=6/15+1/6+1/10+1/21+1/28
=2/5+1/10+1/6+1/21+1/28
=4/10+1/10+1/6+1/21+1/28
=(4+1)/10+1/6+1/21+1/28
=5/10+1/6+1/21+1/28
=1/2+1/6+1/21+1/28
=3/6+1/6+1/21+1/28
=(3+1)/6+1/21+1/28
=4/6+1/21+1/28
=2/3+1/21+1/28
=14/21+1/21+1/28
=(14+1)/21+1/28
=15/21+1/28
=5/7+1/28
=20/28+1/28
=(20+1)/28
=21/28
=3/4