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GATE 2018 ME (ME1) – Question 11

Engineering Mathematics · Probability and Statistics: Probability, conditional probability, sampling theorems · 1 mark · Multiple choice

A box contains four red, four green and four blue balls. Three are drawn successively at random without replacement. Probability that all three are red is ______.

  1. 1/72
  2. 1/55
  3. 1/36
  4. 1/27

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Correct answer: (B) 1/55

Explanation

The successive red-draw probabilities are 4/12, 3/11 and 2/10. Their product is $24/1320=1/55$ (B).