A bag contains 2 red. 3 green and 2 blue balls, Two balls are drawn at random. What is the probability that none of the balls drawn is blue?
1. 2/7
2. 11/21
3. 10/21
4. 5/7
1. 2/7
2. 11/21
3. 10/21
4. 5/7
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Correct Answer – Option 3 : 10/21
Given:
A bag contains 2 red 3 green and 2 blue balls, Two balls are drawn at random.
Formula Used:
Probability = favorable outcome/total outcome
Calculation:
None of the balls drawn is blue, this can only happen when the two balls drawn at random are either red and green or both.
Total number of balls = 2 + 3 + 2 = 7
⇒ Number of ways of drawing 2 balls out of 7 = 7C2 = (7 × 6) / (2 × 1) = 42/2 = 21
Number of balls other than blue = 5
⇒ Number of ways of drawing 2 balls out of 5 = 5C2 = (5 × 4) / (2 × 1) = 20/2 = 10
∴ Required Probability = 10/21