Question

three coins are tossed.what are probability of getting: at most two heads;at least two heads;exactly two heads.

Answer 1

Given that 3 coins are tossed. 

The possible outcomes = 2^3 = 8.

(1) The probability of getting atmost two heads:

n(E) = {TTT,TTH,THT,HHT,THH,HTT,THH}. = 7.

Therefore P(E) = n(E)/n(S)

                         = 7/8.


(2)the probability that getting At least two heads:

n(E) = {HHH,HHT,HTH,THH}

       = 4.

Therefore P(E) = n(E)/n(S)

                         = 4/8

                         = 1/2.



(3) The probability of getting exactly two heads:

n(E) = {HHT,THH,HTH}

       = 3.


Therefore P(E) = n(E)/n(S)

                         = 3/8.



Hope this helps!