shovan85 wrote:danjuma wrote:A drawer contains 8 socks and 2 socks are selected at random without replacement. What is the probability that both socks are black?
1. The probability is < 0.2 that the first sock is black.
2. The probability is more than 0.8 that the first sock is white.
Can one use the probability formula for this type of question?
Thank you
I have some genuine concerns about this questions.
First of all we do not know that drawer contains only Black and White socks. There can be Red also
1: P(B) < 0.2
Total choices 8
then P(B) < 1.6/8 so there can be only 1 or 0 black sock.
How can we say that both of the socks will be black as at best there will be 1 black sock.
2: P(W) > 0.8
then P(W) > 6.4/8 so there can be only 7 or 8 white socks.
How can we say that both of the socks will be black as at best there will be 1 black sock. (if any other color is not there)
Combining both also we are not getting two black socks in any case. If there is no possibility of getting two socks then how can we draw 2 black socks. I think both are individually sufficient ... totally confused
IMO
D
shovan your guess is correct
But look at both the statements
first statement is about availability of getting 1 black sock or zero sock
second statement is about the availability os 7 white socks or 8 socks.
So from this statement you can infer that there are no other colour socks in it.
So there is no possiblilty of getting two black socks i.e., the probability of getting a two black sock is zero.
This what we have in the question.
So choosing an option using the both the statement would be wise .
I hope its correct to choose using both the statements.
cheers
