RS Aggarwal Solutions: Probability | Mathematics (Maths) Class 7 (Old NCERT) PDF Download

 Page 1


Q u e s t i o n : 1
A coin is tossed 300 times and we get head : 136 times and tail : 164 times.
When a coin is tossed at random, What is the probability of getting i
a head, i i
a tail?
S o l u t i o n :
Total number of trials = 300
Number of times a head is obtained = 136
Number of times a tail is obtained= 164
i
Probability of getting head =
Numbe r of times heads is obtained
Total number of trials
=
136
300
=
34
75
i i
Probability of getting a tail =
Number of times tails is obtained
Total number of trials
=
164
300
=
41
75
Q u e s t i o n : 2
Two coins are tossed simultaneously 200 times and we get two heads: 58 times, one head: 83 times: 0 head: 59 times.
When two coins are tossed at random, what is the probability of getting i
2 heads, i i
1 head, i i i
0 head?
S o l u t i o n :
Total number of trials = 200
Number of times 2 heads are obtained = 58
Number of times one head is obtained  = 83
Number of times no head is obtained = 59
i
Probability of getting 2 heads =  
Number of times 2 heads have been obtained
Total number of trials 
= 
58
200
=
29
100
i i
Probability of getting 1 head = 
Number of times 1 head has been obtained
Total number of trials 
= 
83
200
i i i
Probability of getting 0 head =  
Number of times head has not been obtained
Total number of trials 
= 
59
200
Q u e s t i o n : 3
A dice is thrown 100 times and the outcomes are noted as given below:
Outcome 1 2 3 4 5 6
Frequency 21 14 18 15 23 9
When a dice is thrown at random, what is the probability of getting a i
3, i i
6, i i i
6, i v
1?
S o l u t i o n :
Total number of trials = 100
Number of times 3 is obtained = 18
Number of times 6 is obtained = 9
Number of times 4 is obtained = 15
Number of times 1 is obtained =  21
i Probability of getting a 3 =
Number of times 3 is obtained
Total number of trials 
=
18
100
=
9
50
ii Probability of getting a 6 =
Number of times 6 is obtained
Total number of trials 
=
9
100
iii Probability of getting a 4 =
Number of times 4 is obtained
Total number of trials 
=
15
100
=
3
20
iv
Q u e s t i o n : 4
In a survey of 100 ladies it was found that 36 like coffee while 64 dislike it.
Out of these ladies, one is chosen at random. What is the probability that the chosen lady i
likes coffee, i i
dislikes coffee?
S o l u t i o n :
Total number of ladies surveyed = 100
Ladies who like coffee = 36
Ladies who do not like coffee = 64
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Page 2


Q u e s t i o n : 1
A coin is tossed 300 times and we get head : 136 times and tail : 164 times.
When a coin is tossed at random, What is the probability of getting i
a head, i i
a tail?
S o l u t i o n :
Total number of trials = 300
Number of times a head is obtained = 136
Number of times a tail is obtained= 164
i
Probability of getting head =
Numbe r of times heads is obtained
Total number of trials
=
136
300
=
34
75
i i
Probability of getting a tail =
Number of times tails is obtained
Total number of trials
=
164
300
=
41
75
Q u e s t i o n : 2
Two coins are tossed simultaneously 200 times and we get two heads: 58 times, one head: 83 times: 0 head: 59 times.
When two coins are tossed at random, what is the probability of getting i
2 heads, i i
1 head, i i i
0 head?
S o l u t i o n :
Total number of trials = 200
Number of times 2 heads are obtained = 58
Number of times one head is obtained  = 83
Number of times no head is obtained = 59
i
Probability of getting 2 heads =  
Number of times 2 heads have been obtained
Total number of trials 
= 
58
200
=
29
100
i i
Probability of getting 1 head = 
Number of times 1 head has been obtained
Total number of trials 
= 
83
200
i i i
Probability of getting 0 head =  
Number of times head has not been obtained
Total number of trials 
= 
59
200
Q u e s t i o n : 3
A dice is thrown 100 times and the outcomes are noted as given below:
Outcome 1 2 3 4 5 6
Frequency 21 14 18 15 23 9
When a dice is thrown at random, what is the probability of getting a i
3, i i
6, i i i
6, i v
1?
S o l u t i o n :
Total number of trials = 100
Number of times 3 is obtained = 18
Number of times 6 is obtained = 9
Number of times 4 is obtained = 15
Number of times 1 is obtained =  21
i Probability of getting a 3 =
Number of times 3 is obtained
Total number of trials 
=
18
100
=
9
50
ii Probability of getting a 6 =
Number of times 6 is obtained
Total number of trials 
=
9
100
iii Probability of getting a 4 =
Number of times 4 is obtained
Total number of trials 
=
15
100
=
3
20
iv
Q u e s t i o n : 4
In a survey of 100 ladies it was found that 36 like coffee while 64 dislike it.
Out of these ladies, one is chosen at random. What is the probability that the chosen lady i
likes coffee, i i
dislikes coffee?
S o l u t i o n :
Total number of ladies surveyed = 100
Ladies who like coffee = 36
Ladies who do not like coffee = 64
( ) ( ) ( ) (
( ) ( )
i Probability of choosing a lady who likes coffee =
Number of ladies who like coffee
Total number of ladies 
=
36
100
=
9
25
ii Probability of choosing a lady who dislikes coffee =
Number of ladies who dislike coffee
Total number of ladies 
=
64
100
=
16
25
( ) ( )