Probability class 9 ____ CBSE

Probability class 9___CBSE

Based upon the CBSE syllabus

1. Probability
Class 9
Done by : Smrithi Jaya

2. Probability

•Probability
•Probability is the study of the uncertainty.
The uncertainty of any doubtful situation
is measured by means of Probability.
•Uses of Probability
•Probability is used in many fields like
Mathematics, Physical Sciences,
Commerce, Biological Sciences, Medical
Sciences, Weather Forecasting, etc.

3. Basic terms related to
Probability


• Random experiment
•If we are doing an experiment and we don't know
the next outcome of the experiment to occur then
it is called a Random Experiment.
•Trial
•A trial is that action whose result is one or more
outcomes. Example :
•Throw of a dice
•Toss of a coin

4. Probability

•Event
•While doing an experiment, an event will be
the collection of some outcomes of that
experiment.
•Example
•If we are throwing a dice then the possible
outcome for even number will be three i.e. 2,
4, 6. So the event would consist of three
outcomes

5. Probability – An Experimental Approach

•Experimental probability is the result of
probability based on the actual experiments
•the probability depends upon the number of
trials and the number of times the required
event happens.
•If the total number of trials is ‘n’ then the
probability of event D happening is

6. Probability – An Experimental Approach



•Examples
•1. If a coin is tossed 100 times out of which 49 times we get head and 51
times we get tail.
•a. Find the probability of getting head.
•b. Find the probability of getting tail.
•c. Check whether the sum of the two probabilities is equal to 1 or not.
•Solution
•a. Let the probability of getting head is P(H)


•Let the probability of getting tail is P(T)


•The sum of two probability is
•= P(H) + P(T)

7. •Impossible Events
•While doing a test if an event is not possible to occur then its
probability will be zero. This is known as an Impossible Event.
•Example
•You cannot throw a dice with number seven on it




•Sure or Certain Event
•While doing a test if there is surety of an event to happen then it is said to
be the sure probability. Here the probability is one.

•Example: 1
•It is certain to draw a blue ball from a bag contain a blue ball only.
•This shows that the probability of an event could be
•0 ≤ P (E) ≤ 1

8. •Example: 2

•There are 5 bags of seeds. If we select fifty seeds at random from each of 5
bags of seeds and sow them for germination. After 20 days, some of the seeds
were germinated from each collection and were recorded as follows:









•What is the probability of germination of
•(i) more than 40 seeds in a bag?
•(ii) 49 seeds in a bag?
•(iii) more than 35 seeds in a bag?
•Solution:
•(i) The number of bags in which more than 40 seeds germinated out of 50 seeds
is 3.
•P (germination of more than 40 seeds in a bag) =
3
5
= 0.6
•(ii) The number of bags in which 49 seeds germinated = 0.
•P (germination of 49 seeds in a bag) =
0
5
= 0
• (iii) The number of bags in which more than 35 seeds germinated = 5.
• So, the required probability =
5
5
=1

Bag 1 2 3 4 5
No. of seeds
germinated
40 48 42 39 41

9. Elementary Event

•Elementary Event
•If there is only one possible outcome of an event to
happen then it is called an Elementary Event.
•Remark
•If we add all the elementary events of an experiment
then their sum will be 1.
•The general form
•P (H) + P (T) = 1
•P (H) + P= 1 (where is ‘not H’).
•P (H) – 1 = P
•P (H) and Pare the complementary events.

10. Example
•What is the probability of not hitting a six in a
cricket match, if a batsman hits a boundary six times
out of 30 balls he played?
•Solution
•Let D be the event of hitting a boundary.



•So the probability of not hitting the boundary will be




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11. Thank you
Done by : Smrithi Jaya