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MathematicsProbabilityConditional probabilityMedium2 minPYQ_2020
MathematicsMediumsingle choice

Box1contains30cards numbered1to30and Box2contains20cards numbered31to50. A box is selected at random and a card is drawn from it. The number on the card is found to be a non-prime number. The probability that the card was drawn from Box1is

Options:

Answer:
B
Solution:

PB1=12=PB2

Box B1 have 20 non-prime numbers 1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30

PNP/B1=2030

Box B1 have 15 non-prime numbers 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50

PNP/B2=1520

Probability of non-prime=PNP.

PNP=PB1.PNP/B1+PB2.PNP/B2

=12·2030+12·1520

PB1/NP=12·203012·2030+12·1520=817

Stream:JEESubject:MathematicsTopic:ProbabilitySubtopic:Conditional probability
2mℹ️ Source: PYQ_2020

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