Secondary school mathematics class 9 rs aggarwal Solutions for Chapter 19 probability

Exercises in Chapter 19 probability Grade 9

Probability Exercise 19

Questions in Probability Exercise 19

A coin is tossed 500 times and we get Heads: 285 times and tails: 215 times.

When a coin is tossed at random, what is the probability of getting

(i) a head?

(ii) a tail?

Two coins are tossed 400 times and we get Two heads: 112 times; one head: 160 times; 0 head: 128 times.

When two coins are tossed at random, what is the probability of getting

(i) 2 heads?

(ii) 1 head?

(iii) 0 head?

Three coins are tossed 200 times and we get Three heads: 39 times; two heads: 58 times;

One head: 67 times; o head: 36 times.

When three coins are tossed at random, what is the probability of getting

(i) 3 heads?

(ii) 1 head?

(iii) 0 head?

(iv) 2 heads?

A die is thrown 300 times and the outcomes are noted as given below:

Outcome	Frequency
1	60
2	72
3	54
4	42
5	39
6	33

When a die is thrown at random, what is the probability of getting a

(i) 3?

(ii) 6?

(iii) 5?

(iv) 1?

In a survey of 200 ladies, it was found that 142 like coffee, while 58 dislike it. Find the probability that a lady chosen at random

(i) likes coffee,

(ii) dislikes coffee.

The percentages of marks obtained by a student in six-unit tests are given below:

Unit test	Percentage of marks obtained
I	53
II	72
III	28
IV	46
V	67
VI	59

A unit test is selected at random. What is the probability that the student gets more than 60% marks in the test?

On a particular day, at a crossing in a city, the various types of 24 vehicles going past during a time interval were observed under:

Types of vehicle	Frequency
Two-wheelers	84
Three-wheelers	68
Four-wheelers	88

Out of these vehicles, one is chosen at random. What is the probability that the chosen vehicle is a two-wheeler?

On one page of a telephone directory, there are 200 phone numbers. The frequency distribution of their unit’s digits is given below:

Unit's digit	Frequency
0	19
1	22
2	23
3	19
4	21
5	24
6	23
7	18
8	16
9	15

One of the numbers is chosen at random from the page. What is the probability that the unit’s digit of the

chosen number is (i) 5? (ii) 8?

The following table shows the blood groups of 40 students in a class.

Blood group	Number of students
A	11
B	9
O	14
AB	6

One student of the class is chosen at random. What is the probability that the chosen student has blood group (i) O? (ii) AB?

12 packets of salt, each marked 2kg, actually contained the following weights (in kg) of salt:

1.950, 2.020, 2.060, 1.980, 2.030, 1.970, 2.040, 1.990, 1.985, 2.025, 2.000, 1.980

Out of these packets, one packet is chosen at random.

What is the probability that the chosen packet contains more than 2kg of salt?

In a cricket match, a batsman hits a boundary 6 times out of 3 balls he plays. Find the probability that

he did not hit a boundary.

An organisation selected 2400 families at random and surveyed them to determine a relationship between the income level and the number of vehicles in a family. The information gathered is listed in the table below:

Monthly income (in ₹)	Number of vehicles per family	-	-	-
-	0	1	2	3 or more
Less than ₹ 25000	10	160	25	0
₹ 25000 - ₹ 30000	0	305	27	2
₹ 30000 - ₹ 35000	1	535	29	1
₹ 35000 - ₹ 40000	2	469	59	25
₹ 40000 or more	1	579	82	88