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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 box, the probability of drawing a black ball is now double of what it was before. Find x Q.4

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Sir give me the best way for solving the problem of question from class 10th ncert of probability chapter of exercise 15.2 of optional chapter how i solve this problem  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 box, the probability of drawing a black ball is now double of what it was before. Find x

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  1. Total number of black balls = x

    Total number of balls = 12

    P(E) = (Number of favourable outcomes/ Total number of outcomes)

    P (getting black balls) = x/12 ——————-(i)

    Now, when 6 more black balls are added,

    Total balls become = 18

    ∴ Total number of black balls = x+6

    Now, P (getting black balls) = (x+6)/18 ——————-(ii)

    It’s given that, the probability of drawing a black ball now is double of what it was before

    (ii) = 2 × (i)

    (x+6)/18 = 2 × (x/12)

    x + 6 = 3x

    2x = 6

    ∴ x = 3

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