11.3. One side of the leaflets is painted in some color, and on the other side, a smiley face is drawn. In front of you lie 4 leaflets: the first one is yellow, the second one is black, the third one has a happy smiley face, and the fourth one has a sad smiley face. You need to verify the statement: "If one side of the leaflet has a happy smiley face, then the other side is painted yellow."

What is the minimum number of leaflets you need to flip to check the truth of this statement? Which ones exactly? (7 points)
# Solution.

The first card does not need to be flipped; if there is a happy smiley face on it, then everything is fine, if it is a sad one, then the statement does not say anything about it.

The second card needs to be flipped; if there is a happy smiley face on it, then the statement is false.

The third card needs to be flipped; if the color is not yellow, then the statement is not true.

The fourth card does not need to be flipped, as the statement does not mention a sad smiley face.

Answer: Two. The second and third.

| criteria | points |
| :--- | :---: |
| 1. correct solution | 7 |
| 2. Each correctly flipped card | 3 |
| 3. Each incorrectly flipped card | -2 |

4