3. 1. Why are numbers placed in this order? 8, 5, 4, 9, 1, 7, 6, 3, 2.

4. 2. There is some sequence given 7, 15, 31, 63, … What is the basis of this sequence?

5. 3. Now Erudit is three times younger than his father. But 5 years ago he was four times younger than his father. How old are Erudit and his father?

6. 4. In the house there are Erudit and his five brothers. All of them are busy. One is playing the piano, another one is reading, the third brother is playing chess, the fourth is watching TV, the fifth is solving a crossword puzzle. What is doing Erudit?

7. 5. Change the place of three matches so that you have three equal squares.

8. 6. Change the place of three matches so that the arrow changes its direction.

9. 7. Matches make an incorrect equation. Change the place of one match so that the equation is correct.

10. 8. A puzzle “A glass with cherry”. Change the place of two matches so that the cherry is not in the glass. It is allowed to change the position of the glass, but it shape can’t be changed.

11. 9. When my father was 31 years old, I was 8 years old. Now my father is two times older than me. How old am I now?

12. 10. One person was asked: ”How old are you?” “A lot” – was the answer. “I am older than some of my relatives six hundred times.” Is it possible?