There are three cards in a box. Both sides of one card are black, both sides of one card are red, and the third card has one black side and one red side. We pick a card at random and observe only one side.
What is the probability that the opposite side is the same colour as the one side we observed?
(A) 3/4
(B) 2/3
(C) 1/2
(D) 1/3


Answer: (B)

Explanation: There are BB RR and BR, total outcome is 3, probability that the opposite side is the same color as the one side we observed:
It is clear that BB and RR will show the same color on opposite side, so favorable outcome will be 2.
Probability will be favorable outcome / total outcome
i.e. 2 / 3.
So, option (B) is correct.

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