# NCERT Solutions for Class 9 Maths Chapter 15 - Probability

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## Chapter 15 - Probability Exercise Ex. 15.1

Solution 1
Number of times batswoman hits a boundary = 6
Total number of balls played = 30 Number of times that the batswoman does not hit a boundary = 30 - 6 = 24 Solution 2
Total number of bags = 11
Number of bags containing more then 5 kg of flour = 7
Required probability = Solution 3
Number days for which the concentration of sulphur dioxide was in the
interval of 0.12 - 0.16 = 2
Total number of days = 30
Required probability  = Solution 4
Number of students having blood group AB = 3
Total number of students = 30
Required probability = Solution 5
Total number of families = 475 + 814 + 211 = 1500

(i) Number of families having 2 girls = 475 (ii) Number of families having 1 girl = 814 (iii) Number of families having no girl = 211
Thus, the sum of all these probabilities is 1.  Thus, the sum of all these probabilities is 1.

Solution 6
Number of students born in August = 6
Total number of students = 40 = Solution 7
Number of times 2 heads come up = 72
Total number of times the coins were tossed = 200 Solution 8
Number of families surveyed = 2400

(i) Number of families earning Rs 10000 - 13000 per month and owning exactly 2 vehicles = 29
Required probability = (ii) Number of families earning Rs 16000 or more per month and owning exactly 1 vehicle = 579
Required probability = (iii) Number of families earning less than Rs 7000 per month and does not own any vehicle = 10
Required probability = (iv)  Number of families earning Rs 13000 - 16000 per month and owning     more than 2 vehicles = 25
Required probability = (v)  Number of families owning not more than 1 vehicle = 10 + 160 + 0 + 305 + 1 + 535 + 2 + 469 + 1
+ 579 = 2062
Required probability = Solution 9
Total number of students = 90

(i)  Number of students who obtained less than 20% marks in the test = 7
Required probability = (ii)  Number of students who obtained marks 60 or above = 15 + 8 = 23
Required probability = Solution 10
Total number of students = 135 + 65 = 200

(i)  Number of students who like statistics = 135
P(student likes statistics) = (ii)  Number of students who do not like statistics = 65
P(student does not like statistics) = Solution 11
Total number of engineers = 40
(i)  Number of engineers living at a distance of less than 7 km form their place of work = 9
Required probability = (ii)  Number of engineers living at a distance of more than or equal to 7 km from their place of work
= 40 - 9 = 31
Required probability = (iii)  Number of engineers living within a distance of km from her place of work = 0
Required probability = 0

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