role of smart class in school

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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.

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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:

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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

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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