# NCERT Class 9 Mathematics Probability Formative Assessment Board Sample Problems (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 1

Twenty four people had a blood test and the results are shown below.

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

AB, A, 0, O, AB, B, O, A, AB, O, B, A

(a) Construct a frequency distribution for the data.

(b) If a person is selected randomly from the group of twenty four people, what is the probability that his/her blood type is not O?

Solution

(a)

 Class Frequency A 5 B 6 AB 6 O 7

(b)

(Rounded to 2 decimal places)

True or False statement

Question 2

Over the past 100 working days, the number of defective bulbs produced by a machine is given in the following table:

 No of Defective parts 0 1 2 3 Days 20 40 12 28

a) The probability that tomorrow output will be defect free is 2.

b) The probability that tomorrow output will have at least 1 defect is 8.

c) The probability that tomorrow output will have more then 2 defect is 30.

d) The probability that tomorrow output will have 3 defects is 28.

Solution

a) True

b) True,

c) False,

d) True.

Multiple choice Questions

Question 3

The probability of the events lies between

a)

b)

c)

d)

Solution (b)

Question 4

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

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

a)

b)

c)

d) None of these

Solution (b)

No of bags having weight more than 5 kg = 7

Total

So

Question 5

A company selected 4000 households at random and surveyed them to find out a relationship between income level and the number of mobile sets in a home. The information so obtained is listed in the following table:

 Monthly income No of Mobile sets 0 1 2 Above2 < 10000 10000 - 14999 15000 - 19999 20000 - 24999 25000 and above

Find the probability of a household earning ₹ 10000 — ₹ 14999 per year and having exactly one mobile set

a) 06

b) 08

c) 04

d) None of these

Solution (a)

Around 240 household are there satisfying the condition

So

Question 6

In the above Question, find the probability of a household earning more than 25000 per year and having exactly 2 mobile set

a) 2

b) 19

c) 12

d) 3

Solution (b)

Around 760 household are there satisfying the condition

So

Question 7

In the above Question, find the probability of a household earning more than 25000 per year and having 2 or more mobile set

a) 245

b) 3

c) 1

d) None of these

Solution (a)

Around 980 household are there satisfying the condition

So

Question 8

In the above Question, find the probability of a household having no mobile set at all?

a)

b)

c)

d) None of these

Solution (a)

Around 30 household are there satisfying the condition

So p

Question 9

In the above Question, find the probability of a household having 3 mobile set and having income less than 10000

a) 1

b) 0

c) 24

d) None of these

Solution (b)

As no household exists like than, so probability is 0

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