Shake Hands, Say Good Evening and Other Problems

Three sticks are used to make a triangle this size. You need to make 4 such triangles - same size and also equilateral. How many sticks do you need? Can you use only six sticks?


There are five of you. Each says Good Evening to everyone else - once. How many Good Evenings are uttered?

What if instead of Good Evenings, each shake hands with everyone else once. How many handshakes are there?

What about if we do this with the whole class - 46 of us?

Did you like the Sound of Numbers Problem? One containers has 2 objects. The other one has an unknown number of objects. Shale both containers and listen to the sound. How many objects are there in the second container?