Multiple choice

A bag contains red white and blue marbles The probability of selecting a red marble is $\displaystyle \frac{2}{15}$ and that of selecting a blue marble is $\displaystyle \frac{4}{15}$ The probability of selecting a white marble is

  1. $\displaystyle \frac{13}{15}$
  2. $\displaystyle \frac{11}{15}$
  3. $\displaystyle \frac{3}{5}$
  4. $\displaystyle \frac{2}{5}$
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C Correct answer
Explanation

Total probability must be 1. P(white) = 1 - (P(red) + P(blue)) = 1 - (2/15 + 4/15) = 1 - 6/15 = 9/15 = 3/5.

AI explanation

Because selecting a red, white, or blue marble are mutually exclusive and exhaustive events, their probabilities must sum to 1. Subtract the given probabilities of red and blue from 1 to find the probability of white. This gives 1 minus 2/15 minus 4/15, which equals 9/15 or 3/5.

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