Probability Math Example 5

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Example 5

medium
A bag contains 4 red, 3 blue, and 5 green marbles. What is the probability of drawing a red or blue marble?

Solution

  1. 1
    Count the total number of marbles: 4+3+5=124 + 3 + 5 = 12.
  2. 2
    Count the favourable outcomes (red or blue): 4+3=74 + 3 = 7.
  3. 3
    Apply the probability formula: P(red or blue)=favourabletotal=712P(\text{red or blue}) = \frac{\text{favourable}}{\text{total}} = \frac{7}{12}.

Answer

P(red or blue)=712P(\text{red or blue}) = \frac{7}{12}
When events are mutually exclusive (a marble cannot be both red and blue), the probability of either event occurring is the sum of their individual probabilities: P(A or B)=P(A)+P(B)P(A \text{ or } B) = P(A) + P(B).

About Probability

Probability is a number between 0 and 1 (inclusive) that measures how likely an event is to occur, where 0 means impossible and 1 means certain.

Learn more about Probability →

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