NCERT Solutions for Class 10 Maths Chapter 15

Important NCERT Questions

PROBABILITY

NCERT Books for Session 2022-2023

CBSE Board and UP Board Others state Board

EXERCISE 15.2

Page No:311

Questions No: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 box, the probability of drawing a black ball is now double of what it was before. Find x.

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Total number of balls = 12

Total number of black balls = x

P (getting a black ball) = x/12

If 6 more black balls are put in the box, then

Total number of balls = 12 + 6 = 18

Total number of black balls = x + 6

P (getting a black ball now) = (x + 6)/18

According to the condition given in the question,

2(x/12) = (x + 6)/18

⇒ 3x = x + 6

⇒ 2x = 6

⇒ x = 3

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