Prof. L. Shridharan
PRACTICE PROBLEMS
1. (a) What is the probability that a leap year selected at random will contain 53 Tuesdays?
(b) What is the probability that a leap year selected at random will contain 53 Sundays or 53 Mondays?
2. A bag contains 8 black, 3 red and 9 white balls. If 3 balls are drawn at random , find the probability that
(a) all are black, (b) 2 are black and 1 is white, (c) 1 of each colour,
(d) the balls are drawn in the order black, red and white, (e) None is red.
3. From a pack of 52 cards, 4 are accidentally dropped. Find the chance that
(a) they will consist of a jack, a queen, a king and an ace.
(b) They are from the same suit.
(c) They are one from each suit.
(d) Two of them are red and two are black.
4. A six figure number is formed by the digits 4, 5, 6, 7, 8 & 9 ; no digit being repeated. Find the chance that the number formed is :
(a) divisible by 5. (b) not divisible by 5.
5. The probability that a contractor will get a plumbing contract is 2/3, and the probability that he will get an electric contract is 5/9. If the probability of getting at least one contract is 4/5, what is the probability that he will get both the contracts?
6. The probability that a management trainee will remain with a company is 0.6. The probability that an employee earns more than Rs.10,000 per month is 0.5. The probability that an employee is management trainee who remained with the company or who earns more than Rs.10,000 per month is 0.7. What is the probability that an employee earns more than Rs.10,000 per month, given that he is a management trainee who stayed with the company?
7. A piece of electronic equipment has two essential parts A and B. In the past, part A failed 30% of the times, part B failed 20% of the times and both failed simultaneously 5% of the times. Assuming that both parts