18
If you have sticks which measure 1, 2, 3, 4, 5, 6, 7, 8 and 9 cm (one of each). How many different triangles can you make using three of the sticks?
You need to climb ten stairs. At every stair, you can either take one step up or you can jump two steps up.
In how many different ways you can climb 10 stairs?
