Math Puzzles 2

Puzzle 1: Which number replaces the question mark?

Puzzle 2: Which number replaces the question mark?

Puzzle 3: Which number replaces the question mark?

If 1 =3

    2 = 6

    3 = 9

    4 = 12

Then, 5 = ?

Puzzle 4: Which number replaces the question mark?

11 x 11 = 4

22 x 22 = 16

33 x 33 = ?

Puzzle 5: Which number replaces the question mark?

2, 15, 41, 80, ?