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Find probabilities from coloured objects

Probability of selecting a particular colour from a collection of equally likely objects is the number of objects of that colour divided by the total number of objects, expressed as a fraction and, when appropriate, as a decimal or percentage. The calculation distinguishes the likelihood of an individual object from the likelihood of a colour and supports comparison of events and use of complementary probabilities; dependent multi-step selections and more advanced probability models are not included.

Detailed Explanation: Find probabilities from coloured objects

When all objects are equally likely to be chosen, use:

Probability=number of objects of the colourtotal number of objects\text{Probability}=\frac{\text{number of objects of the colour}}{\text{total number of objects}}

Example: A bag contains 5 red counters, 3 blue counters, and 2 green counters. What is the probability of choosing a blue counter?

  1. Count the blue counters.
    There are 33 blue counters.

  2. Find the total number of counters.

5+3+2=10 5+3+2=10

  1. Write the probability as a fraction.

P(blue)=310 P(\text{blue})=\frac{3}{10}
  1. Convert if needed.
    The fraction 310\frac{3}{10} is equal to (0.3)(0.3), or (30%)(30\%).

So, the probability of choosing a blue counter is:

310=0.3=30%\boxed{\frac{3}{10}=0.3=30\%}

Only count the objects with the colour you want in the numerator. Count all the objects in the denominator.

Learn by doing: Find probabilities from coloured objects

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    Probability - Shapes, One Set of Two Shapes, Two Colors - Pick One by Color, To Percent

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