1. ## Challenge #1

The following figure is composed of 17 matches to form 6 squares geometrically similar to each other:

Remove only 3 matches in order to get only 4 squares geometrically similar to each other.

* Adapted from the book Distractions mathématiques (Montréal - 1977).

In Desafio #1 - Challenge #1 - Desafios Matemáticos! - O site da Matemática

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2. If you remove the three horizontal sticks in the middle you do get four squares

3. Hello, Prof Paulo!

I don't trust the wording of this problem.
Besides, the solution is too simple.

The following figure is composed of 17 matches to form 6 squares geometrically similar to each other.
Redundant . . . all squares are geometrically similar.

Code:
       ----- ----- -----
|     |     |     |
|     |     |     |
----- ----- -----
|     |     |     |
|     |     |     |
----- ----- -----
There are eight squares which are geometrically similar:
. . six 1-by-1 squares,
. . two 2-by-2 squares.

Remove only 3 matches in order to get only 4 squares geometrically similar to each other.
Solution:

Code:
       -----       -----
|     |     |     |
|     |     |     |
-----       -----
|     |     |     |
|     |     |     |
-----       -----

Perhaps the author meant congruent squares?

4. It's correct pankaj e Soroban!