UPSC NDA I 2015 Mathematics Solved Paper

Consider the two given boxes
Box I → Red (2) Black(3)
Box II → Red (3) Black(2)
Probability of different colored balls in box 1 is

2×3

5C2

=

6

10

=

3

5

Probability of different colored balls in box 2 is

3×2

5C2

=

6

10

=

3

5

So if one box is chosen at random, the probability of different colored ball is

1

2

×

3

5

+

1

2

×

3

5

=

3

5