+130511 The probability of getting heads on any flip is (1/2)....this is the same probability of getting tails on any flip.
And the probability of getting 3 heads is (1/2)3......and he probability of getting tails on the rest of the flips is (1/2)15 ...... and we can choose any 3 of the 18 flips to have the heads occur....so we have
C(18,3)(1/2)3(1/2)15 = about .0003 = about .03%
+130511 The probability of getting heads on any flip is (1/2)....this is the same probability of getting tails on any flip.
And the probability of getting 3 heads is (1/2)3......and he probability of getting tails on the rest of the flips is (1/2)15 ...... and we can choose any 3 of the 18 flips to have the heads occur....so we have
C(18,3)(1/2)3(1/2)15 = about .0003 = about .03%
