9709 P61 - Nov 2012 - Q5
3042
A company set up a display consisting of 20 fireworks. For each firework, the probability that it fails to work is 0.05, independently of other fireworks.
(i) Find the probability that more than 1 firework fails to work.
The 20 fireworks cost the company $24 each. 450 people pay the company $10 each to watch the display. If more than 1 firework fails to work they get their money back.
(ii) Calculate the expected profit for the company.
