(i) Probability of getting a red ball in the first draw =
18
8
=
9
4
The ball is replaced after the first draw.
∴ Probability of getting a red ball in the second draw =
18
8
=
9
4
Therefore, probability of getting both the balls red =
9
4
×
9
4
=
81
16
=0.19
(ii) Probability of getting first ball black =
18
10
=
9
5
The ball is replaced after the first draw.
Probability of getting second ball as red =
18
8
=
9
4
Therefore, probability of getting first ball as black and second ball as red =
9
5
×
9
4
=
81
20
=0.24
(iii) Probability of getting first ball as red =
18
8
=
9
4
The ball is replaced after the first draw.
Probability of getting second ball as black =
18
10
=
9
5
Therefore, probability of getting first ball as black and second ball as red =
9
4
×
9
5
=
81
20
Therefore, probability that one of them is black and other is red = Probability of getting first ball black and second as red + Probability of getting first ball red and second ball black
(i) Probability of getting a red ball in the first draw =
18
8
=
9
4
The ball is replaced after the first draw.
∴ Probability of getting a red ball in the second draw =
18
8
=
9
4
Therefore, probability of getting both the balls red =
9
4
×
9
4
=
81
16
=0.19
(ii) Probability of getting first ball black =
18
10
=
9
5
The ball is replaced after the first draw.
Probability of getting second ball as red =
18
8
=
9
4
Therefore, probability of getting first ball as black and second ball as red =
9
5
×
9
4
=
81
20
=0.24
(iii) Probability of getting first ball as red =
18
8
=
9
4
The ball is replaced after the first draw.
Probability of getting second ball as black =
18
10
=
9
5
Therefore, probability of getting first ball as black and second ball as red =
9
4
×
9
5
=
81
20
Therefore, probability that one of them is black and other is red = Probability of getting first ball black and second as red + Probability of getting first ball red and second ball black
Answers & Comments
Total number of balls =18
Number of red balls =8
Number of black balls =10
(i) Probability of getting a red ball in the first draw =
18
8
=
9
4
The ball is replaced after the first draw.
∴ Probability of getting a red ball in the second draw =
18
8
=
9
4
Therefore, probability of getting both the balls red =
9
4
×
9
4
=
81
16
=0.19
(ii) Probability of getting first ball black =
18
10
=
9
5
The ball is replaced after the first draw.
Probability of getting second ball as red =
18
8
=
9
4
Therefore, probability of getting first ball as black and second ball as red =
9
5
×
9
4
=
81
20
=0.24
(iii) Probability of getting first ball as red =
18
8
=
9
4
The ball is replaced after the first draw.
Probability of getting second ball as black =
18
10
=
9
5
Therefore, probability of getting first ball as black and second ball as red =
9
4
×
9
5
=
81
20
Therefore, probability that one of them is black and other is red = Probability of getting first ball black and second as red + Probability of getting first ball red and second ball black
=
81
20
+
81
20
=
81
40
=0.49
Answer:
Total number of balls =18
Number of red balls =8
Number of black balls =10
(i) Probability of getting a red ball in the first draw =
18
8
=
9
4
The ball is replaced after the first draw.
∴ Probability of getting a red ball in the second draw =
18
8
=
9
4
Therefore, probability of getting both the balls red =
9
4
×
9
4
=
81
16
=0.19
(ii) Probability of getting first ball black =
18
10
=
9
5
The ball is replaced after the first draw.
Probability of getting second ball as red =
18
8
=
9
4
Therefore, probability of getting first ball as black and second ball as red =
9
5
×
9
4
=
81
20
=0.24
(iii) Probability of getting first ball as red =
18
8
=
9
4
The ball is replaced after the first draw.
Probability of getting second ball as black =
18
10
=
9
5
Therefore, probability of getting first ball as black and second ball as red =
9
4
×
9
5
=
81
20
Therefore, probability that one of them is black and other is red = Probability of getting first ball black and second as red + Probability of getting first ball red and second ball black
=
81
20
+
81
20
=
81
40
=0.49