Question

Probability of getting blue ball is 2/3 from a bag containing 6 blue and 3 red balls.12 red balls are added in the bag then find the probability of getting :
1.a blue ball
2.a red ball

Answer 1

Total number of balls=6+3=9

12 red balls are added.

New number of red balls=12+3=15

Number of total balls=9+12=21

Probability of red ball=15/21

=5/7

Probability of blue ball =6/21

=2/7

Answer 2

1.  P(getting a blue ball)=$\dfrac{6}{21} =\dfrac{2}{7}$

2.  P(getting a red ball)=$\dfrac{15}{21} =\dfrac{5}{7}$

Step-by-step explanation:

Given,

Probability of getting blue ball = $\dfrac{2}{3}$

Total number of balls = Number of blue balls + Number of red balls

= 6 + 3 = 9

To find, the probability of getting: 1. a blue ball  = ? 2. a red ball = ?

After, 12 red balls are added in the bag

Total number of balls = 9 + 12 = 21

Total number of possible outcomes = 21

1. a blue ball  

Blue ball = 6

Number of favourable outcomes = 6

∴ P(getting a blue ball)=$\dfrac{6}{21} =\dfrac{2}{7}$

2. a red ball

Red ball = 3 + 12 = 15

Number of favourable outcomes = 15

∴ P(getting a red ball)=$\dfrac{15}{21} =\dfrac{5}{7}$