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Bebras 2021 - Level 3 Question 12

BEBRAS · Bebras 2021 - Level 3

Question 12

The beavers like using Bomino tiles. These tiles are decorated by colouring cells grey on a $3\times3$ grid according to these rules:

- Every grey cell must share an edge or a vertex with at least one other grey cell.
- Every grey cell shares an edge with at most one other grey cell.
- A tile with $n$ grey cells is called an $n$-Bomino.
- Two tiles are considered the same if one can be rotated or flipped to obtain the other.

Below are examples of a 2-Bomino and a 4-Bomino.

Question illustration

How many different 3-Bomino tiles are there?
  1. 3
  2. 4
  3. 5
  4. 6