Verified Solution • 2025–26 Session moderate

QJEEAdv24Ma38a5: JEE Advanced 2024 Mathematics - Class 12 JEEAdv24Ma38a5 Solution: A bag contains balls out of which 3 balls are white, 6 balls…

A bag contains NN balls out of which 3 balls are white, 6 balls are green, and the remaining balls are blue. Assume that the balls are identical otherwise. Three balls are drawn randomly one after the other without replacement. For i=1,2,3i=1,2,3 , let Wi,GiW_i, G_i , and BiB_i denote the events that the ball drawn in the ith i^{\text {th }} draw is a white ball, green ball, and blue ball, respectively. If the probability P(W1∩G2∩B3)=25NP\left(W_1 \cap G_2 \cap B_3\right)=\frac{2}{5 N} and the conditional probability P(B3∣W1∩G2)=29P\left(B_3 \mid W_1 \cap G_2\right)=\frac{2}{9} , then NN equals ________.

Step-by-Step Verified Solution

3 White

6 Green

(N−9) Blue

 Given P(W1∩G2∩B3)=25N and P(B3∣W1∩G2)=29⇒P(B3∩W1∩G2)P(W1∩G2)=29⇒25N×N×(N−1)3×6=29⇒N=11

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