Find the probability of the following events in eleven tosses of a fair coin using binomial

probability?
a. Exactly 4 heads up
b. at least 9 heads up

1 answer

P(h) = P(t) = 1/2

expand the binomial ... (h + t)^11

Pascal's triangle can help with the term coefficients

a. 11C7 (h^4 t^7)

b. 11C0 (h^11) + 11C1 (h^10 t) + 11C2 (h^9 t^2)