Total Number of socks = 4 pairs= 8 socks
Number of red socks = 4
Number of black socks = 4
Probability of pulling a red sock from the bag the first time = [tex] \frac{4}{8}= \frac{1}{2} [/tex]
Since the sock is placed back in the bag before pulling a sock again, the number of socks remains the same.
So,
Probability of pulling a red sock from the bag the second time = [tex] \frac{4}{8}= \frac{1}{2} [/tex]
And
Probability of pulling a red sock from the bag the third time = [tex] \frac{4}{8}= \frac{1}{2} [/tex]
Therefore, the probability of pulling a red sock 3 times from the bag = [tex] \frac{1}{2}* \frac{1}{2}* \frac{1}{2}= \frac{1}{8} [/tex]