A survey showed that 40% of investors invest in at least two companies in order to

diversify their risk.

Calculate an approximate probability that more than 100 investors have invested

in at least two companies in a random sample of 300 investors.

(a) A recruitment company places adverts in three publications with probabilities of

0.2, 0.3 and 0.5 respectively.

The probability that the recruitment company gets an enquiry from an advert in

the first publication is 0.001. The probabilities for the other two publications are

0.002 and 0.004 respectively.

Given that the company has just received an enquiry, calculate the probability

that it came from an advert in the first publication