256.Three Heads in a Row
★★★combinatoricsSIG
A fair coin is tossed five times. What is the probability that at least three heads appear consecutively at some point?
Sign in to submit an answer and track it toward your stats.
Sign inHint
Enumerate by where the run of three starts, and take care not to count sequences with longer runs twice.
Want timed drills, mental math, and a market-making game too? Try the full practice suite →