Hello, buenogilabert!

Person tosses a fair coin until it lands heads, then person does the same.

In the end, they toss it 10 times.

What is the probability that person tossed it only once?

tossed once and got a Head,

. . then tossed nine times to grt a Head.

We want: .

. . . . . . . . . . . . . . . .

Therefore: .