A bag contains lsquo x rsquo red balls lsquo x 2 rsquo pink balls Two balls are randomly drawn from ...........

Quantitative Aptitude ( CCS) Probability

A bag contains ‘x’ red balls , ‘x+2’ pink balls. Two balls are randomly drawn from the bag and the probability that a red and a blue ball are drawn is 4/21. Find the total number of balls in the bag.

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Explanation:

Total number of balls in the bag = x+x+2+x+5
= 3x+7
Probability that a red and a blue ball are drawn = (xC1*(x+2)C1)/(3x+7)C2 = 4/21
2x(x+2)/(3x+7)(3x+6) = 4/21
=> x = 14
The number of balls in the bag = 14*3+7 = 49

Hence, option 4 is the correct answer.