Question

. A bag contains 4 black balls and 6 red balls, if one ball is drawn at random, then the probability of getting a red ball is​

Answer 1

Correct option is

D

5

2

​

 

There are 2 possible cases: first ball drawn is red or is black.

∴ P(second ball red | first ball drawn is black) =  

4+8

4

​

=  

3

1

​

 

∴ P(second ball red | first ball drawn is red) =  

6+6

4+2

​

=  

2

1

​

 

Hence, the probability of the second ball being red  

=  P(first ball black)×P(second ball red | first ball black)+P(first ball red)×P(second ball red | first ball red)

=  

10

6

​

×  

3

1

​

+  

10

4

​

×  

2

1

​

 

=  

5

2

​

 

This is the required probability.