Four model workers entered the conference room to attend the symposium, shaking hands with each other once and _ _ _ _ _ times. Sign the autograph book in turn, with _ _ _ _
( 1)(4- 1)×4÷2,
= 12÷2,
=6 (times);
(2)4×3×2× 1=24 (species);
Answer: shake hands six times and sign the autograph book in turn. There are 24 different signature sequences.
So the answer is: 6,24.