How many sequences contain exactly three heads when you flip a coin five times?

Question

2
15
10
8
12

my answer was 15 ,but that was incorrect

Answer 1

So you want the sequence
HHHTT or permutations of that

So we have 5 things to arrange, 3 alike of one kind, and 2 alike of another.
Number of ways = 5!/(3!2!) = 10