NCERT Solutions Class 9th Maths Chapter – 15 Probability Exercise 15.1
| Textbook | NCERT |
| Class | 9th |
| Subject | Mathematics |
| Chapter | 15th |
| Chapter Name | Probability |
| Category | Class 9th Maths |
| Medium | English |
| Source | Last Doubt |
NCERT Solutions Class 9th Maths Chapter – 15 Probability Exercise 15.1
Chapter – 15
Probability
Exercise 15.1
Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 1 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: According to the question, |
| Ncert Solution Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 2 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 Solution: Total numbers of families = 1500 (i) Numbers of families having 2 girls = 475 (ii) Numbers of families having 1 girl = 814 (iii) Numbers of families having 0 girls = 211 |
| Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 3 3. Refer to Example 5, Section 14.4, Chapter 14. Find the probability that a student of the class was born in August. Solution:
Total numbers of students in the class = 40 |
| Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 4 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. Solution: Number of times 2 heads come up = 72 |
| Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 5 5. An organisation selected 2400 families at random and surveyed them to determine a relationship between income level and the number of vehicles in a family. The information gathered is listed in the table below:
Suppose a family is chosen. Find the probability that the family chosen is (i) earning ₹10000 – 13000 per month and owning exactly 2 vehicles. Solution: Total number of families = 2400 (ii) Number of families earning ₹16000 or more per month and owning exactly 1 vehicle = 579 (iii) Number of families earning less than ₹7000 per month and does not own any vehicle = 10 (iv) Number of families earning ₹13000-16000 per month and owning more than 2 vehicles = 25 (v) Number of families owning not more than 1 vehicle = 10 + 160 + 0 + 305 + 1 + 535 + 2 + 469 + 1 + 579 | ||||||||||||||||||||||||||||||||||
| Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 6 Ncert Solution Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 6 6. Refer to Table 14.7, Chapter 14. (i) Find the probability that a student obtained less than 20% in the mathematics test. Solution:
Total number of students = 90 (i) Number of students who obtained less than 20% in the mathematics test = 7 (ii) Number of students who obtained marks 60 or above = 15 + 8 = 23 |
| Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 7 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 chosen at random (i) likes statistics, (ii) does not like it. Solution: Total number of students = 135 + 65 = 200 (ii) Number of students who do not like statistics = 65 |
Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 8 8. Refer to Q.2, Exercise 14.2. 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? (iii) Within 1/2 km from her place of work? Solution: The distance (in km) of 40 engineers from their residence to their place of work were found as follows: 5, 3, 10, 20, 25, 11, 13, 7, 12, 31, 19, 10, 12, 17, 18, 11, 32, 17, 16, 2, 7, 9, 7, 8, 3, 5, 12, 15, 18, 3, 12, 14, 29, 6, 15, 15, 7, 6, 12 Total numbers of engineers = 40 (i) Number of engineers living less than 7 km from their place of work = 9 the probability that an engineer lives less than 7 km from her place of work = 9/40 (ii) Number of engineers living more than or equal to 7 km from their place of work = 40-9 = 31 probability that an engineer lives more than or equal to 7 km from her place of work = 31/40 (iii) Number of engineers living within 1/2 km from their place of work = 0 the probability that an engineer lives within 1/2 km from her place of work = 0/40 = 0 |
Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 9 9. Activity : Note the frequency of two-wheelers, three-wheelers 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. Solution: Lets assume a case :- |
Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 10 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 divisible by 3? Remember that a number is divisible by 3, if the sum of its digits is divisible by 3. Solution: Let’s assume these values |
| Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 11 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 4.98 5.04 5.07 5.00 Find the probability that any of these bags chosen at random contains more than 5 kg of flour. Solution: Total number of bags present = 11 Number of bags containing more than 5 kg of flour = 7 the probability that any of the bags chosen at random contains more than 5 kg of flour = 7/11 |
| Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 12 12. In Q.5, Exercise 14.2, you were asked to prepare a frequency distribution table, regarding the concentration of sulphur dioxide in the air in parts per million 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.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 0.04 Solution: Total number of days in which the data was recorded = 30 days Numbers of days in which sulphur dioxide was present in between the interval 0.12-0.16 = 2 the probability of the concentration of sulphur dioxide in the interval 0.12-0.16 on any of these days = 2/30 = 1/15 |
Ncert Solutions Class 9th Maths (Chapter – 15) Exercise – 15.1 Question No. 13 13. In Q.1, Exercise 14.2, you were asked to prepare a frequency distribution table regarding the blood groups of 30 students of a class. Use this table to determine 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. Solution: Total numbers of students = 30 Number of students having blood group AB = 3 the probability that a student of this class, selected at random, has blood group AB = 3/30 = 1/10 |