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Bag A: 3 red, 2 black. Bag B: 4 red, 5 black. A bag picked at random, ball drawn. P(red ball) is
A47/90
B7/14
C3/5
D1/2
Answer & Solution
Correct answer: A. 47/90
1. P(Bag A) = P(Bag B) = 1/2.
2. P(red | A) = 3/5; P(red | B) = 4/9.
3. P(red) = (1/2)(3/5) + (1/2)(4/9) = 3/10 + 4/18 = 27/90 + 20/90.
4. = 47/90.
_Source: ICAI BoS Foundation Paper 3, Ch 15 'Probability', p.13_
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