A 3 cm diameter coin can pass through a 2 cm diameter hole, without forcing or tearing it.
We make a round hole of 2 cm in diameter in the center of a sheet of paper. The sheet of paper is folded on itself 3 or 4 times as shown in the image, using the hole as a vertex, thus obtaining a funnel. Gently deposit the coin inside the funnel. If it does not go to the first, close the top part of the funnel gently and gently.