Points to Remember

Probability

Points to Remember

• If we are able to predict the exact outcome of an experiment then it is called deterministic experiment.

• If we cannot predict the exact outcome of an experiment then it is called random experiment.

• Sample space S for a random experiment is the set of all possible outcomes of a random experiment.

• An event is a particular outcome or combination of outcomes of an experiment.

• Empirical probability states that probability of an outcome is close to the percentage of occurrence of the outcome.

• If the likelyhood of happening of two events are same then they are known as equally likely events.

• If two events cannot occur simultaneously in single trial then they are said to be mutually exclusive events.

• Two events E and E′ are said to be complementary events if P (E ) + P (E′) = 1 .

• An event which is sure to happen is called certain or sure event. The probability of a sure event is always one.

• An event which never happen is called impossible event. The probability of an impossible event is always zero.

Probability

Answers:

Exercise 9.1

1. 1/7

2. 3/13

3. 1/2

4.(i) 5/24  (ii) 1/8 (iii) 2/3

5. 1/4

6.(i) 0  (ii) 1/12 (iii) 1

7. 1/280

8. 1/5

9. 3/4

Exercise 9.2

1. 0.9975

2. 209/400

 3. 15/8

4. 0.28

5.(i) 1/6 (ii) 43/75 (iii) 1/75

Exercise 9.3

1. (4) 2. (2) 3. (1) 4. (4) 5. (1) 6. (4) 7. (4) 8. (4) 9. (1) 10. (2)