Need help with probability
My sock drawer contains two red socks, two white socks, and two blue socks. For three days in a row, I pull out two socks out of my sock drawer at random. What is the probability that I get matching socks on all three days?
There are a total of 6 socks in the drawer, so the number of ways to choose 2 socks at random is (6 C 2) = 15.
To find the probability of getting matching socks on any given day, we can count the number of ways to choose 2 socks of the same color, and divide by the total number of ways to choose 2 socks.
There are 3 ways to choose 2 red socks, 3 ways to choose 2 white socks, and 3 ways to choose 2 blue socks. So the total number of ways to get matching socks on any given day is 3 + 3 + 3 = 9.
Therefore, the probability of getting matching socks on any given day is 9/15 = 3/5.
To find the probability of getting matching socks on all three days, we can use the multiplication rule of probability. That is, the probability of two independent events A and B both occurring is the product of their individual probabilities:
P(A and B) = P(A) × P(B)
In this case, we want the probability of getting matching socks on all three days, which are independent events. So the probability is:
P(getting matching socks on all three days) = (3/5) × (3/5) × (3/5) = 27/125
Therefore, the probability of getting matching socks on all three days is 27/125.
Justin:
1 - To get a matching pair of any of the 3 colors, you have:
2 / 6 x 1 / 5 = 2 / 30
But, you have 3 matching pairs. Therefore:
3 x 2 / 30 = 6 / 30 = 1 / 5 - probability of getting a matching pair on day 1
2 - On day 2, you would go through exactly the same procedure all over again, which means:
The probability is exactly the same as day 1 = 1 / 5
3 - On day 3, exactly the same = 1 / 5
4 - So, to get a matching pair 3 days in a row, you have:
The probability = (1 / 5)^3 = 1 / 125
Yes, your solution is correct. The probability of getting a matching pair of any of the 3 colors on day 1 is indeed 1/5, and this probability remains the same for day 2 and day 3. Therefore, the probability of getting a matching pair 3 days in a row is (1/5)^3, which is 1/125. Well done!