21 into 20 best min fragment found: 7
  Cut up 21 sticks of length 20 like this:
    3 x (10 + 10)
    6 x (9 + 11)
    6 x (8 + 12)
    6 x (7 + 13)
  Reassemble as 20 sticks of length 21 like this:
    6 x (10 + 11)
    6 x (9 + 12)
    6 x (8 + 13)
    2 x (7 + 7 + 7)