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A bag contains 5 red balls and some black balls. If the probability of drawing a black ball from the bag is twice that of a red ball. Find the number of black balls in the bag.
  • a)
    7
  • b)
    12
  • c)
    10
  • d)
    15
Correct answer is option 'C'. Can you explain this answer?
Most Upvoted Answer
A bag contains 5 red balls and some black balls. If the probability of...
To solve this problem, let's assume the number of black balls in the bag is 'x'.

Given that the probability of drawing a black ball is twice that of a red ball, we can set up the following equation:

Probability of drawing a black ball = 2 * Probability of drawing a red ball

The total number of balls in the bag is 5 red balls + x black balls. Therefore, the total probability of drawing either a red or a black ball is equal to 1.

To find the probability of drawing a red ball, we divide the number of red balls by the total number of balls:

Probability of drawing a red ball = 5 / (5 + x)

To find the probability of drawing a black ball, we divide the number of black balls by the total number of balls:

Probability of drawing a black ball = x / (5 + x)

Since the probability of drawing a black ball is twice that of a red ball, we can write the equation as:

x / (5 + x) = 2 * (5 / (5 + x))

Now, we can solve this equation to find the value of x.

Cross-multiplying, we get:

x = 2 * 5

x = 10

Therefore, the number of black balls in the bag is 10.

So, the correct answer is option 'C', which is 10.
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Community Answer
A bag contains 5 red balls and some black balls. If the probability of...
Let the no. of black balls = x
Total no. of balls = x + 5
Probability of drawing a black ball = 
Probability of drawing a red ball =
According to question,
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A bag contains 5 red balls and some black balls. If the probability of drawing a black ball from the bag is twice that of a red ball. Find the number of black balls in the bag.a)7b)12c)10d)15Correct answer is option 'C'. Can you explain this answer?
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