Multiple choice

Which information are necessary to answer the questions asked- A bag contains balls of only three different colours i.e., red, yellow and green. 3 balls are drawn randomly. What is the probability that the balls drawn are of three different colours? A. The no. of yellow balls is two more than the no. of red balls. B. The Sum of the no. of yellow and green balls is three times the no. of red balls. C. The ratio of the no. of red balls to that of green balls is 3 : 4.

  1. A and either B or C

  2. Any two of them

  3. Only A and C together

  4. Question can’t be answered even after using all the informations.

  5. All statements are required
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Let r, y, g be numbers of red, yellow, green balls. A: y = r + 2. B: y + g = 3r. C: r/g = 3/4. Using A and C: g = 4r/3, then from A: y = r + 2. Need B to get actual values: r+2+4r/3 = 3r, giving r=6, y=8, g=8. Total = 22. P(3 different) = (6×8×8)/(22×21×20) = 384/9240 = 8/175. All three statements are required.

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