# Ex 15.2, 4 (Optional) - Chapter 15 Class 10 Probability

Last updated at June 29, 2018 by Teachoo

Last updated at June 29, 2018 by Teachoo

Transcript

Ex 15.2, 4 A box contains 12 balls out of which x are black. If one ball is drawn at random from the box, what is the probability that it will be a black ball? If 6 more black balls are put in the bag, the probability of drawing a black ball is now double of what is was before. Find x. Given, Total balls in the box = 12 Black balls in the box = x Probability of drawing a black ball = (๐๐ข๐๐๐๐ ๐๐ ๐๐๐๐๐ ๐๐๐๐๐ )/(๐๐๐ก๐๐ ๐๐ข๐๐๐๐ ๐๐ ๐๐๐๐๐ ) = ๐ฅ/12 If 6 more black balls are put in the box, Total number of balls = 12 + 6 = 18 Number of black balls = x + 6 Probability of drawing a black balls = (๐ฅ + 6)/18 Given, after adding 6 balls, probability of drawing a black ball is double of what it was before. โด New Probability = 2 ร Old probability (๐ฅ + 6)/18 = 2 ร ๐ฅ/12 (๐ฅ + 6)/18 = ๐ฅ/6 6 [(๐ฅ + 6)/18] = ๐ฅ (๐ฅ + 6)/3 = ๐ฅ ๐ฅ+6 = 3๐ฅ 6 = 3๐ฅโ๐ฅ 6 = 2๐ฅ 2๐ฅ = 6 ๐ฅ" = " 6/2 โด ๐ = ๐

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