Footnote

On average, you'd have to go through about 3000 pieces before finding your first match.

• Ten puzzles at 2500 pieces each makes 25,000 pieces total.

• To be guaranteed of finding the piece to fit any one side of the piece in your hand, you would have to go through all 25,000 remaining pieces (okay 24,999, but we're talking ballpark). You will probably find the piece before then, though, and on average you would have to go through half the pile to do it. This means that on average you will have to test 12,500 pieces before finding a match.

• Most of the pieces have four sides, which increases the probably that a tested piece would fit one of the four sides of the original one. This means, on average, you will only have to go through one fourth of the pieces you would need to got through for just one side, or 3125 pieces.

• But some pieces are edges with fewer than four sides, and it is impossible to tell how many there are without knowing the aspect ratio of each of the puzzles. This confounds us at the moment, so we'll just fudge it and round to the nearest thousand.