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NCERT Solutions for Class 9 Maths Chapter 15 Probability

NCERT Solutions for Class 9 Maths Chapter 15 Probability covers the empirical (experimental) approach to probability, based on the frequency of outcomes actually observed in trials of an experiment.

Overview of Topics & Subtopics (Click to Jump)

1. Empirical Probability

Short Note:

• Experimental (Empirical) Probability of an event E = (Number of trials in which E happened) ÷ (Total number of trials).

• As the number of trials in an experiment increases, the experimental probability tends to get closer to a theoretical value, but at the Class 9 level, probability is studied purely from actual recorded data.

• The probability of an event always lies between 0 and 1, inclusive: 0 ≤ P(E) ≤ 1.

2. Applications

Short Note:

• Empirical probability is calculated from real experiments such as tossing coins, throwing dice, or from survey/statistical data such as results of matches, family sizes, or student marks.

NCERT Textbook Exercise Questions

A coin is tossed 1000 times, and the outcomes are: Head: 455 times, Tail: 545 times. Find the probability of getting (i) a head, (ii) a tail.
Answer: (i) P(head) = 455/1000 = 0.455.
(ii) P(tail) = 545/1000 = 0.545.
1500 families with 2 children were selected randomly, and the following data recorded: 2 girls – 475, 1 girl & 1 boy – 814, no girl – 211. Compute the probability of a family chosen at random having 2 girls.
Answer: Total families = 1500. Families with 2 girls = 475. P(2 girls) = 475/1500 = 19/60 ≈ 0.317.
In a cricket match, a batswoman hits a boundary 6 times out of 30 balls she plays. Find the probability that she did not hit a boundary.
Answer: P(hit a boundary) = 6/30 = 1/5. P(did not hit a boundary) = 1 − 1/5 = 4/5.
The percentage of marks obtained by a student in 12 unit tests are given. Find the probability that the student gets more than 70% marks in a test, if there are 4 such tests out of 12.
Answer: P(more than 70% marks) = 4/12 = 1/3.
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More for this chapter

Class 9 › Mathematics › Probability
Chapter notesRead the chapterPractice MCQsCheck what you rememberChapter test10 questions on one pageOnline testTest 1, 2 and 3, one question at a timePYQPrevious year questionsStudy materialPDF notes
Topics in this chapter: Empirical ProbabilityApplications