JEE Advanced2015MathematicsProbabilityActual
Let n 1 a n d n 2 be the number of red and black balls, respectively, in box I. Let n 3 a n d n 4 be the number of red and black balls, respectively, in box II. A ball is drawn at random from box I and transferred to box II. If the probability of drawing a red ball from box I, after this transfer, is 1 3 , then the correct options(s) with the possible values of n 1 a n d n 2 is(are)
Options
- An 1 = 4 a n d n 2 = 6
- Bn 1 = 2 a n d n 2 = 3
- Cn 1 = 10 a n d n 2 = 20
- Dn 1 = 3 a n d n 2 = 6
Correct answer
C. n 1 = 10 a n d n 2 = 20
Step-by-step solution
Probability = n 1 n 1 + n 2 ⋅ n 1 - 1 n 1 + n 2 - 1 + n 2 n 1 + n 2 ⋅ n 1 n 1 + n 2 - 1 = 1 3 ⇒ n 1 n 1 - 1 + n 2 n 1 n 1 + n 2 ( n 1 + n 2 - 1 ) = 1 3 ⇒ n 1 = 10 , n 2 = 20 or n 1 = 3 , n 2 = 6