Maths : Probability: 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)

Tags : Probability | Maths , 9th Maths : UNIT 9 : Probability

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9th Maths : UNIT 9 : Probability : Points to Remember | Probability | Maths

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