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.`

Options

A. `x = 3`
B. `x = 5`
C. `x = 6`
D. `x = 7`

Answer

A

Explanation

balls in the box `12` balls

let black balls be`x`

let e event be taking out black ball `x`

no of possibilities= `12`

`P(e)=x/12`

now, 6 more black balls put in the box

balls in box`= 12+6 = 18`balls

black balls`x+6`

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