Puzzle

Answer all the questions below and press submit to see how many you got right.

id: 20389

How many different 4-digit numbers can be formed from the digits 1 and 2 if each digit can be used once, several times or not at all?

id: 20448

Starting on A1 what is the maximum number of squares on a regular chess board that a knight can move to sequentially without visiting any field twice?

id: 20422

What is the probability that three thrown coins all land on heads? (Answer as a simplified fraction a/b.)