An urn contains 6 red balls and some black balls

Question

One ball is selected and the probability it is red is 3/11. The number of black balls is?

Answer 1

The probability to select a red ball is P(R) = 6/(6+n)

Here, n is the number of black balls.

P(R) = 6/(6 + n)

3/11 = 6/(6 + n)

3(6 + n)  = 11(6)

18 + 3n = 66

3n = 48

n = 16

Therefore, the number of black ball are 16.