balls are drawn from a bag containing ewual number of black and white balls ,each ball being replaced before drawing other .In 2550 drawings ,1080 black and 1232 white balls have been drawn. do you suspect some bias on the part of drawer?
Answers
Answer:
Correct option is
D
0.19, 0.24, 0.49
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