A bag contains 3 red marbles and 4 blue marbles. A marble is taken out from the bag and replaced. Another marble is taken from the bag. Work out the probability that the two marbles taken from the bag are the same colour.

Question

Hanna Richardson

Mathematics

19 December, 07:25

A bag contains 3 red marbles and 4 blue marbles. A marble is taken out from the bag and replaced. Another marble is taken from the bag. Work out the probability that the two marbles taken from the bag are the same colour.

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Answers (2)

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Tabitha Briggs · Answer 1

I think 2/7 would be the probability

Bruce Watts · Answer 2

A bag contains 3 red marbles and 4 blue marbles. a marble is taken at random and replaced. Another marble is taken from the bag. Work out the probability that the two marbles taken from the bag are the same color.

Total number of marbles in the bag is 3 + 4 = 7. The problem asks for the probability of (RR) or (BB). It's worthy to note we are replacing the balls after each draw, which means we always have 7 to draw from Since each draw is independent, we take the product of each event for the total event probability.

P (RR) = 3/7 * 3/7 = 9/49

P (BB) = 4/7 * 4/7 = 16/49

We want to know P (RR) + P (BB)

P (RR) + P (BB) = 9/49 + 16/49 = 25/49