A bag has 7 red balls and 5 white balls. A ball is drawn, replaced, and then a second ball is drawn. Find the probability that the two balls are of different colours.
Answer and explanation
Correct answer: B.
- Step 1: Two orders work: red then white, or white then red.
- Step 2: .
Answer
.
Why not the others: : it counts only one order, red then white. : it gives the probability of two of the same colour. : it adds the single probabilities.
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