what do you guys think the answer is?

[meghamehta15]

2. A fair coin is tossed 5 times. What is the probability of getting at least three heads on consecutive tosses?

[Stuart@KaplanGMAT]

Exactly 3 consecutive heads out of 5 tosses:

HHHTT
HHHTH
THHHT
TTHHH
HTHHH

Exactly 4 consecutive heads out of 5 tosses:

HHHHT
THHHH

Exactly 5 consecutive heads out of 5 tosses:

HHHHH

That's 8 desired outcomes out of 2^5 possibilities, so 8/32 or 1/4.

[meghamehta15]

thank you so much for your answer, but I was wondering if you know of a way to answer this question without having to list down the various combinations? Is there a formula?

[Stuart@KaplanGMAT]

I'm sure we could figure one out, but because of the "consecutive" part it's going to be more work than just counting them.