1.

In the first box there are 5 white, 3 red and 2 green balls. In the second box there are 2 white, 4 red and 3 green balls. We take one ball out of the first box and transfer it to the second box, and then we draw three balls from the second box. If all the balls drawn from the second box were different colour, what is the probability that the ball we transferred from the first to the second box was red?

Answer»

Answer:

Correct option is

A

16

7

For the bag A we can see that there are 2 white, 3 red and 2 BLACK BALLS. SIMILARLY, from bag B we have 4 white, 2 red and 3 black balls.

Probability of choosing a white and then a red ball from bag B is given by =

9

C

2

4

C

1

×

2

C

1

Probability of choosing a white ball then a red ball from bag A is given by =

7

C

2

2

C

1

×

3

C

1

So, the probability of getting a white ball and then a red ball from bag B is given by

9

C

2

4

C

1

×

2

C

1

+

7

C

2

2

C

1

×

3

C

1

9

C

2

4

C

1

×

2

C

1

=

7

2

+

9

2

9

2

=

18+14

2×7

=

16

7


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