Question

A bag contains 4 red and some black balls, A
ball is picked from the bag at random. If the
probability of it being a black ball is twice that
of a red ball, then the number of black balls in
that bag is​

Answer 1

Answer:

Number of red balls = 4

Probability (black ball) = 2 × Probability (red ball)

Step-by-step explanation:

Probability = Favorable outcomes/Total outcomes

Calculation:

Let the number of black balls be ‘x’

According to the question,  

x/(4 + x) = 2 × 4/(4 + x)

⇒ x = 8

∴ Number of black balls = 8

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