A box contains 12 balls of which some are red in colour. If 6 more red balls are put in the box and a ball is drawn at random, the probability of drawing a red ball doubles than what it was before. Find the number of red balls in the bag.
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Answered by
8
let number of red balls original was X, and probability of getting it out is X ÷12.
now when adding 6 more in the box ,total number of ball goes up to 18 ,,the probability of getting a red ball is X + 6 ÷18 now
{X+6}÷18=2{x}÷12
on calculation ,, red ball originally comes out to be 3
now when adding 6 more in the box ,total number of ball goes up to 18 ,,the probability of getting a red ball is X + 6 ÷18 now
{X+6}÷18=2{x}÷12
on calculation ,, red ball originally comes out to be 3
Answered by
7
Answer:
The number of red balls is 3.
Step-by-step explanation:
Total number of balls in the box = 12
Red balls in the box = x
Probability of getting a red ball = Number Of Red Balls / Total Number Of Balls In The Box
= x / 12
If 6 more red balls are added in the box,
Total number of red balls = 12 + 6 = 18
Number of red balls = x + 6
Probability of getting a red ball = x + 6 / 18
According to the question:
New probability = 2 * Old Probability
= x + 6 / 18 = 2 * x / 12
= x + 6 / 18 = x / 6
= 6(x + 6 / 18) = x
= 6(x + 6) = 18x
= x + 6 = 18x / 6
= x + 6 = 3x
= 6 = 3x - x
= 6 = 2x
∴ x = 6 / 2 = 3
Therefore, the number of red balls is 3.
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