Let the number of black socks = b
So the question can be rephrased as b/36 * (b-1)/35 = ?
Stmt 1 : The probability of the 1st sock being black = b/36 = 4/9
Cross multiply and you get b = 16
Hence we know that the 16 is the total number of black socks
This information helps us calculate the exact probability of getting 2 black socks. Hence stmt 1 is sufficient.
Stmt 2 : Let the number of white socks be w hence, w = b+4
This information does not help us arrive at the exact probability of getting 2 black socks because we are not told whether the 36 socks consist of only black and white socks or whether there are more colours as well.
Since we can not derive exact information,this statement is insufficient.
Answer : A
So the question can be rephrased as b/36 * (b-1)/35 = ?
Stmt 1 : The probability of the 1st sock being black = b/36 = 4/9
Cross multiply and you get b = 16
Hence we know that the 16 is the total number of black socks
This information helps us calculate the exact probability of getting 2 black socks. Hence stmt 1 is sufficient.
Stmt 2 : Let the number of white socks be w hence, w = b+4
This information does not help us arrive at the exact probability of getting 2 black socks because we are not told whether the 36 socks consist of only black and white socks or whether there are more colours as well.
Since we can not derive exact information,this statement is insufficient.
Answer : A