Problem-Solving and Data AnalysisEasy–MediumProbability of not drawing a colour
Problem-Solving and Data Analysis practice question
A bag contains 20 marbles: 8 red, 6 blue, and 6 green. If one marble is drawn at random, what is the probability that it is NOT green?
Answer: 7/10 or 0.7 or 14/20
Not green: 8 + 6 = 14 of 20, so 14/20 = 7/10. (Or 1 − 6/20.)
Common wrong answers
- If you answered 3/10
- 3/10 is the probability of green, not of not-green.
- If you answered 6/14
- 6/14 compares green to not-green rather than to all 20.
- If you answered 2/3
- 2/3 counts colours (two of three) instead of marbles.
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