binomial distributions

Question

Find the probability of having 2,3, or 4 successes in five trials of a binomial experiment in which the probability of success is 40% Round to the nearest tenth of a percent.

Answer 1

There's a formula for the probability of having exactly k successes in n trials of a binomial experiment with probability p of success. You should look it up in your textbook (or other learning material). It's

P(X = k) = (_nC_k)p^k(1-p)^(n-k)

Simply calculate the values for k = 2, 3 and 4 and add them up.