1/2+1/6+1/12+1/20+1/30+1/3+1/50简便计算？

1/2+1/6+1/12+1/20+1/30+1/3+1/50
=1/2+1/20+1/30+1/3+1/50+1/6+1/12
=11/20 + 11/30 + 1/50 + 1/4
=33/60+ 22/60 + 4/200 + 50/200
= 44/60 + 54/200
=444/600 +162/600
=606/600
= 303/300
= 1又3/300

=1/2+1/(2×3)+1/(3x4)+……+1/(6x7)+1/(7×8)
=1/2+1/2-1/3+1/3-1/4+1/4-1/5+……-1/7+1/7-1/8
=1-1/8
=7/8