1) If there are 12 persons in a party, and if each two of them shake hands with each other, how many handshakes happen in the party?

2) In how many ways a committee of 5 members can be selected from 6 men and 5 women, consisting of 3 men and 2 women?

3) A polygon has 44 diagonals. Find the number of its sides.

4) There are 4 letters and 4 addressed envelopes corresponding to each of the letters. Find the number of ways in which all letters can be put in wrong envelopes.

5) How many triangles can be formed by joining the vertices of a hexagon?

7) 3 6 24 ? 144 576

7) 575 552 533 ? 507

8) 220 96 347 77 516 60 ?

9) 5 17 13 41 29 ? 61

10) 9 19 39 ? 159