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  1. Chapter 15 Class 10 Probability
  2. Serial order wise
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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 = (๐‘๐‘ข๐‘š๐‘๐‘’๐‘Ÿ ๐‘œ๐‘“ ๐‘๐‘™๐‘Ž๐‘๐‘˜ ๐‘๐‘Ž๐‘™๐‘™๐‘ )/(๐‘‡๐‘œ๐‘ก๐‘Ž๐‘™ ๐‘›๐‘ข๐‘š๐‘๐‘’๐‘Ÿ ๐‘œ๐‘“ ๐‘๐‘Ž๐‘™๐‘™๐‘ ) = ๐‘ฅ/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 = (๐‘ฅ + 6)/18 Given, after adding 6 balls, probability of drawing a black ball is double of what it was before. โˆด New Probability = 2 ร— Old probability (๐‘ฅ + 6)/18 = 2 ร— ๐‘ฅ/12 (๐‘ฅ + 6)/18 = ๐‘ฅ/6 6 [(๐‘ฅ + 6)/18] = ๐‘ฅ (๐‘ฅ + 6)/3 = ๐‘ฅ ๐‘ฅ+6 = 3๐‘ฅ 6 = 3๐‘ฅโˆ’๐‘ฅ 6 = 2๐‘ฅ 2๐‘ฅ = 6 ๐‘ฅ" = " 6/2 โˆด ๐’™ = ๐Ÿ‘

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