1) A jigsaw puzzle is put together by successively joining pieces that fit together into
blocks. A move is made each time a piece is added to a block, or when two blocks are
joined. Use a strong induction to prove that no matter how the moves are carried
out, exactly n − 1 moves are required to assemble a puzzle with n pieces.
Let n = number of pieces
n + 1n = 2n ← number of pieces assemble into one.
n + 1n = 1 assembly
(n + 1n) + 1n(third piece) = 2nd assembly........and so on a=until finished.
Granting there are three piece to be assembled as in the above. 3 piece with only 2 acted of assembly and finished the Job.
So: n - 1 ← Total assembly
therefore logically after assembling all the n pieces there is always one(1) piece the first piece not included in counting to whom the second piece is assembled into. So total Assemble piece minus the first piece to whom all the assembled pieces is put into until finished. → n - 1