Answer:
For each draw, the chances of getting a blue marble are 3 of 7; the chances of getting a red are 4 of 7.
The chances of drawing a blue on both draws is (3/7)^2 or 9/49, and the chances of getting red on both draws is (4/7)^2 or 16/49. But there are other possible outcomes which have to be considered to come to the correct answer.
There are 4 possible outcomes, as follows (although the chances of these outcomes are different):
Comb Chances
RR …….. 16/49
RB …….. 12/49
BR …….. 12/49
BB ……… 9/49
total …….. 49/49
So we can say that the chances of drawing red marbles on each draw are 16/49, and the chances of drawing blue ones on each draw are 9/49. But what about the chances of drawing either both red OR both blue?
I believe we can simply add the 2 probabilities together to come up with a probability of
Ken Warren, former Accountant at Various (1977-2016)
Answered February 6, 2020
Originally Answered: There is a bag filled with 3 blue and 4 red marbles. A marble is taken at random from the bag, the colour is noted and then it is replaced. Another marble is taken at random. What is the probability of getting 2 of the same colour?
Probability of two reds = 4/7 x 4/7 = 16/49 = 32.65%
Probability of two blues = 3/7 x 3/7 = 9/49
Probability of the same colour = 25 / 49 = 51.0 %
Explanation: