1/2*5+1/5*8+1/8*11+1/11*14+1/14*17

1/2*5+1/5*8+1/8*11+1/11*14+1/14*17

1/(2*5)+1/(5*8)+1/(8*11)+1/(11*14)+1/(14*17)
=(1/3)[(1/2-1/5)+(1/5-1/8)+(1/8-1/11)+(1/11-1/14)+(1/14-1/17) ]
=(1/3)( 1/2 -1/17)
=5/34