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MathematicsProbabilityTotal probability/Bay's TheoremMedium2 minPYQ_2015
MathematicsMediummultiple choice

Letn1 and n2be the number of red and black balls, respectively, in box I. Letn3and n4be the number of red and black balls, respectively, in box II.
One of the two boxes, box I and box II, was selected at random and a ball was drawn randomly out of this box. The balls was found to be red. If the probability that this red ball was drawn from box II is13, then the correct option(s) with the possible values ofn1, n2, n3and n4is(are)

Question diagram: Let n 1 a n d n 2 be the number of red and black balls, resp

Options:(select one or more)

Answer:
A, B
Solution:



13= 12n3n3+n412 n1n1+n2+ n3n3+n4
13= n3n3+n4n1n1+n2+ n3n3+n4
(i) RHS 520520+36= 1414+12= 141+24=13
(ii)RHS 10601060+39=1616+13= 1612=13
(iii)525814+525= 1547+15= 1520+735=727
(iv)525618+525= 155+315= 15815=15×158=38.

Stream:JEE_ADVSubject:MathematicsTopic:ProbabilitySubtopic:Total probability/Bay's Theorem
2mℹ️ Source: PYQ_2015

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