Question

There are 3 urns A, B and C each containing a total of 10 marbles of which 2, 7 and 4 respectively are red. One of the urns is selected randomly and a marble is drawn from the selected urn. It is found that the marble is red. What is the probability that the red marble is taken from urn B

Answer 1

Answer:  7/13

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Explanation:

We know that the marble selected is red, so we don't need to focus on the other colors.

7 red marbles are in urn B out of 2+7+4 = 13 total red marbles.

The probability the red marble came from urn B is therefore 7/13