NCERT Class 9 Solutions: Probability (Chapter 15) Exercise 15.1-Part 1

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Equation of probability

Equation of Probability

Equation of probability

Q-1 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.

Solution:

Total numbers of balls

Numbers of boundary

Numbers of time she didn't hit boundary

Probability she did not hit a boundary (P)

Q-2 1500 families with 2 children were selected randomly and the following data were recorded:

Number of Girls in Family Are Given
Number of girls in family are given

Number of girls in a family

2

1

0

Number of families

475

814

211

Compare the probability of family, chosen at random, having

I. 2 girls

II. 1 girl

III. No girl

Solution I:

Total numbers of families

Numbers of families having girls

Probability

Solution II:

Total numbers of families

Numbers of families having girls

Probability

Solution III:

Total numbers of families

Numbers of families having no girls

Probability

Sum of the probability =

Yes, the sum of these probabilities is

Q-3 In a particular section of class IX, 40 students were asked about the months of their birth and the following graph was prepared for the data so obtained. Find the probability that a student of class was born in August.

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Created with Highcharts 4.2.5Month of birthNumber of studentsMonth of birth Vs Number of studentsMonth of birth Vs Number of studentsJan.Feb.Mar.Apr.May.June.July.Aug.Sep.Oct.Nov.Dec02468Sep.Month of birth Vs Number of students: 3

Solution:

Total numbers of students

Numbers of students born in August

Required probability