Question

a bag contains 15 white and some black balls the probability of drawing a black ball from the bag is thrice that of drawing a white ball,find the no.of black balls in the bag

Answer 1

Answer:

Step-by-step explanation:

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Answer 2

Answer -

The number of black balls in the bag is 45.

Step-by-step explanation -

Given,

Number of white balls = $15$

Let the number of black balls be $x$ .

So, the total outcome = $15+x$

Let the probability of white balls be $P_{1}$ and that of black balls be $P_{2}$.

Then,

Probability of white balls, $P_{1}=\frac{15}{15+x}$

Probability of black balls, $P_{2}=\frac{x}{15+x}$

According to question,

$\implies P_{2}=3\:P_{1}$

$\implies\frac{x}{15+x}=3\times\frac{15}{15+x}$

$\implies\frac{x}{15+x}=\frac{45}{15+x}$

$\implies x=45$