Multiple choice

A bag contains red, white and blue pencils. The probability of selecting a red pencil is $\dfrac {2}{13}$ and that of selecting a blue pencil is $\dfrac {4}{13}$. Find the probability of selecting a white pencil.

  1. $\dfrac {6}{13}$
  2. $\dfrac {7}{13}$
  3. $\dfrac {3}{5}$
  4. $\dfrac {2}{5}$
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B Correct answer
Explanation

Total probability must be 1. P(Red) + P(Blue) + P(White) = 1. 2/13 + 4/13 + P(White) = 1. 6/13 + P(White) = 1. P(White) = 7/13.

AI explanation

The sum of probabilities for all possible outcomes in a sample space must equal 1. We subtract the probability of selecting a red pencil and a blue pencil from 1, which is 1 minus 2/13 minus 4/13. This leaves a remaining probability of 7/13 for selecting a white pencil.

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