Three unbiased coins are tossed. What is the probability

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Three unbiased coins are tossed. What is the probability of getting at most 2 heads ?

∵ n(S) = (2)³ = 8
E = Event of getting 0, or 1 or 2 heads
= {TTT, TTH, THT, HTT, HHT, HTH, THH}
⇒ n(E) = 7
∴ P(E) = n(E)/n(S) = 7/8