role of smart class in school
Cbse-spot.blogspot.com
1
Class IX Chapter 15 – Probability
Maths
Exercise 15.1 Question 1:
In a cricket math, a batswoman hits a boundary 6 times out of 30 balls she plays.
Find the probability that she did not hit a boundary.
Answer:
Number of times the 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
Question 2:
1500 families with 2 children were selected randomly, and the following data were recorded: Number of girls in a family
2
1
0
Number of families
475
814
211
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.
Cbse-spot.blogspot.com
2
Answer:
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
Therefore, the sum of all these probabilities is 1.
Question 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:
Cbse-spot.blogspot.com
3
Find the probability that a student of the class was born in August.
Answer:
Number of students born in the month of August = 6
Total number of students = 40
Question 4:
Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:
Outcome
3 heads 2 heads
1 head
No head
Frequency
23
72
77
28
If the three coins are simultaneously tossed again, compute the probability of 2 heads coming up.
Answer:
Number of times 2 heads come up = 72
Cbse-spot.blogspot.com
4
Total number of times the coins were tossed = 200
Question 5:
An organization selected 2400 families at random and surveyed them to determine a relationship between income level and
1
Class IX Chapter 15 – Probability
Maths
Exercise 15.1 Question 1:
In a cricket math, a batswoman hits a boundary 6 times out of 30 balls she plays.
Find the probability that she did not hit a boundary.
Answer:
Number of times the 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
Question 2:
1500 families with 2 children were selected randomly, and the following data were recorded: Number of girls in a family
2
1
0
Number of families
475
814
211
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.
Cbse-spot.blogspot.com
2
Answer:
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
Therefore, the sum of all these probabilities is 1.
Question 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:
Cbse-spot.blogspot.com
3
Find the probability that a student of the class was born in August.
Answer:
Number of students born in the month of August = 6
Total number of students = 40
Question 4:
Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:
Outcome
3 heads 2 heads
1 head
No head
Frequency
23
72
77
28
If the three coins are simultaneously tossed again, compute the probability of 2 heads coming up.
Answer:
Number of times 2 heads come up = 72
Cbse-spot.blogspot.com
4
Total number of times the coins were tossed = 200
Question 5:
An organization selected 2400 families at random and surveyed them to determine a relationship between income level and