Throw four coins with different numbers, and at least two coins are facing up. How many situations are there?

There are two situations on each side, and the total * * * is 2 4 =16.

1 All tails of species

1 4 face up (choose one face up and the other face up)

At least 2 pieces face up = total number-less than or equal to 1 pieces face up =16-1-4 =11species.

Or, if you calculate directly,

2 pieces face up, 4 pieces are optional, 2 pieces 4C2=6 kinds.

Three heads, four heads, four heads

3 heads up, 1 species

At least 2 pieces are face up =6+4+ 1= 1 1 species.