Suppose a plane has 500 seats. From experience, it's known that 10% of people who have bought the ticket do not show up. Now, 550 tickets have been sold for one flight. What is the probability that there will be enough seats for all people who turn up? Hint: Use the normal approximation to the binomial distribution.
X ~ B(n, p) and if n is large, then X is approximately N(np, npq)
X ~ B(550,0.9) = N(495,49.5)
B==> P(X<=500) = N==> P(X<500.5)
the output is 0.78 but i am not sure. .. any help?