SEBA Class 9 Mathematics Chapter 15 Probability

SEBA Class 9 Mathematics Chapter 15 Probability Solutions, SEBA Class 9 Maths Textbook Notes in English Medium, SEBA Class 9 Mathematics Chapter 15 Probability Solutions in English to each chapter is provided in the list so that you can easily browse throughout different chapter Assam Board SEBA Class 9 Mathematics Chapter 15 Probability Notes and select needs one.

SEBA Class 9 Mathematics Chapter 15 Probability

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Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. SEBA Class 9 Mathematics Chapter 15 Probability Question Answer. These solutions are part of SCERT All Subject Solutions. Here we have given SEBA Class 9 Mathematics Chapter 15 Probability Solutions for All Subject, You can practice these here.

Probability

Chapter – 15

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.

Ans: Let E be the event of hitting the boundary. 

The, 

∴ Probability of not hitting the boundary

= 1-Probability of hitting the boundary 

= 1 – P(E) = 1 – 0.2 = 0.8

2. 1500 families with 2 children were selected randomly, and the following data were recorded: 

Compute the probability of a family, chosen at random, having

(i) 2 girls

(ii) 1 girl

(iii) No girl.

Also check whether the sum of these probabilities is 1. 

Ans: Total number of families = 475 + 814 + 211 = 1500

(i) Probability of a family, chosen at random, having 2 girls

(ii) Probability of a family, chosen at random, having 1 girl 

(iii) Probability of a family, chosen at random, having no girl 

Sum of these probabilities 

Hence the sum is checked.

3. Refer to Example 5, section 14.4, Chapter 14. Find the prob- ability that a student of the class was born in August.

Or

In a particular section of Class IX, 40 students were asked about the months of their birth, the fol-lowing graph was prepared for the data obtained.

Ans: Total number of students born in the year 

= 3+4+2+2+5+1+2+6+3+4+4+4 = 40 

Number of students born in August = 6 

∴ Probability that a student of the class was born in Au- 

4. Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:

If the three coins are simultaneously tossed again, compute the probability of 2 heads coming up.

Ans: Total number of times the three coins are tossed = 200

Number of times when 2 heads appear = 72

5. An organisation selected 2400 families at random and sur-veyed them to determine a relationship between income level and the number of vehicles in a family. The infor-mation gathered is listed in the table below:

Suppose a family is chosen. Find the probability that the family chosen is

(i) earing Rs. 10000-13000 per month and owing exactly 2 vehicles.

(ii) earing Rs. 16000 or more per month and owing exactly 1 vehicle.

(iii) earing less than Rs. 7000 per month and does not own any vehicle.

(iv) earing Rs. 13000-16000 per month and owing more than 2 vehicles.

(v) owing not more than I vehicle.

Ans: Total number of families selected = 2400

(i) Number of families earing Rs. 10000 – 13000 per month and owing exactly 2 vehicles = 29 

∴ Probability that the family chosen is earing Rs. 10000-

(ii) Number of families earing Rs. 16000 or more per month and owing exactly 1 vehicle = 579

∴ Probability that the family chosen is earing Rs. 16000 or more per month and owing exactly 1 vehicle 

 (iii) Number of families earing less than Rs. 7000 per month and does not own any vehicle = 10 

∴ Probability that the family chosen is earing less than Rs. 7000 per month and does not own any vehicle 

(iv) Number of families earing Rs. 1300-16000 per month and owing more than 2 vehicles = 25 

∴ Probability that the family chosen is earing Rs. 13000-16000 per month and owing more than 2 vehicles

(v) Number of families owing not more than I vehicle = Number of families owing 0 vehicle + Number of fami-lies owing 1 vehicle 

=(10+0+1+2+1) + (160+305+535+469+579) 

= 14+2048-2062 

∴ Probability that the family chosen owns not more than 1 

6. Refer to Table 14.7, chapter 14.

(i) Find the probability that a student obtained less than 20% in the mathematic test.

(ii) Find the probability that a student obtained marks 60 or above.

Ans: Total number of students = 90

(i) Number of students obtaining less than 20% in the maths-ematics test = 7

Probability that a student obtained less than 20% in maths- 

(ii) Number of students obtaining marks 60 or above =15+8 = 23

7. To know the opinion of the students about the subject statistics, a survey of 200 students was conducted. The data is recorded in the following table:

Find the probability that a student student chosen at random

(i) likes statistics.

(ii)does not like it.

Ans: Total number of students = 200

(i) Number of students who like statistics = 135

∴ Probability that a student chosen at random likes statistics 

(ii) Number of students who do not like statistics = 65

∴ Probability that a student chosen at random does not like it

Aliter: Probability that a student chosen at random does like statistics

= 1-probability that a student chosen at random likes statistics

8. Refer to Q.2. Ex. 14.2

The distance (in km) of 40 female engineers from their resi-dence to their place of work were found as follows:

What is the empirical probability that an engineer lives:

(i) less than 7 km from her place of work?

(ii) more than or equal to 7 km from her place of work?

Ans: Total number of female engineers = 40

(i) Number of female engineers whose distance (in km) from their residence to their place of work is less than 7 km = 9 

∴ Probability that an engineer lives less than 7 km from her 

(ii) Number of female engineers whose distance (in km) from their residence to their place of work is more than or equal to 7 km = 31.

∴ Probability that an engineer lives more than or equal to 7 km

Aliter: Probability that an engineer lives more than or equal to 7 km from her place of residence.

= 1-probability that an engineer lives less than 7 km from her place work.

(iii) Number of female engineers whose distance (in km) from 

9. Activity: Note the frequency of two wheelers, three wheel- ers and four wheelers going past during a time interval, in front of your school gate. Find the probability that any one vehicle out of the total vehicles you have observed is a two- wheeler.

Ans: Students, do yourself.

10. Activity: Ask all the students in your class to write a 3-digit number. Choose any student from the room at random. What is the probability that the number written by her/him is divis-ible by 3? Remember that a number is divisible by 3. if the sum of its digits is divisible by 3.

Ans: Students, do yourself.

11.  Eleven bags of wheat flour, each marked 5 kg, actually contained the following weights of flour (in kg):

4.97, 5.05, 5.08, 5.03. 5.00. 5.06. 5.08. 5.04, 5.07, 5.00 

Find the probability that any of these bags chosen at randcon contains more than 5 kg of flour.

Ans: Total number of bags of wheat flour = 11

Number of bags of wheat flour containing more than 5 kg of flour = 7 

∴ Probability that any of the bags, chosen at random, contains 

12. In Q. 5, Exercise 14.2 given below, you were asked to pre- pare a frequency distribution table, regarding the con-centration of sulphur dioxide in the air in parts per mil-lion of a certain city for 30 days. Using this table, find the probability of the concentration of sulphur dioxide in the interval 0.12-0.16 on any of these days.

“A study was conducted to find out the concentration of sulphur dioxide in the air in parts per million (ppm) of a certain city. The data obtained for 30 days is as follows: 

0.03, 0.08, 0.08, 0.09, 0.04, 0.17, 0.16, 0.05, 0.02, 0.06, 0.18, 0.20, 0.11, 0.08, 0.12, 0.13, 0.22, 0.07, 0.08, 0.01, 0.10, 0.06, 0.09, 0.18, 0.11, 0.07, 0.05, 0.07, 0.01, 0.4”

Ans: Total number of days = 30 

Number of days on which the concentration of sulphur diox- ide is in the interval 0.12 0.16 = 2 

∴ Probability that the concentration of sulphur dioxide is in the

13. In Q. 1, Exercise 14.2 given below, you were asked to prepare a frequency distribution table regarding the blood groups of 30 students of a class. Use this table to deter-mine the probability that a student of this class, selected at random, has blood group AB. 

“The blood groups of 30 students of Class VIII are recorded as follows:

A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O, A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O. 

Represent this data in the form of a frequency distribution table. Find out which is the most common and which is the rarest blood group among these students.”

Ans: Total number of students = 30

Number of student = 30 

Number of students having blood groups AB = 3 

∴ Probability that a student of this class, selected at ran-dom, has blood group