Statisticshard · Past Paper
A bag contains 5 red and 'n' blue balls. If the probability of drawing a blue ball is double that of a red ball, find n.
A5
B10
C15
D20
✓ Correct Answer: B — 10
P(Blue) = n/(n+5). P(Red) = 5/(n+5). n/(n+5) = 2 * 5/(n+5) => n = 10.
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