What is probability of at most one head on tossing 3 coins?

Answer 1

There are 8 permutations of three coins. Of those, three of them have only one head, so the probability of throwing only one head is 3 in 8, or 0.375.

However, you said, "at most", and that includes the permutation that does not include any heads at all, so the probability of throwing at most one head in three coins is 4 in 8, or 0.5.

T T T *

T T H *

T H T *

T H H

H T T *

H T H

H H T

H H H