The Addition Rule of Probability: Definition & Examples


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Grace, Avery, and Noah are creating a maze for their pet gerbil, Sam. Grace bets that Sam will turn left when first entering the maze. Avery bets that Sam will turn right, and Noah bets that Sam will go straight. If there's an equal chance of Sam taking one of the given paths, then what is the probability that Grace or Noah will be correct?

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1. Melissa collects data on her college graduating class. She finds out that of her classmates, 60% are brunettes, 20% have blue eyes, and 5% are brunettes that have blue eyes. What is the probability that one of Melissa's classmates will be a brunette or have blue eyes?

2. Karen takes her group of third grade students out for ice cream. There is a total of 30 students. 13 of the students enjoy chocolate ice cream, 12 of the students enjoy strawberry ice cream, and 5 students enjoy vanilla ice cream. When asked which two ice creams are their favorite, 8 students said they enjoy chocolate and strawberry ice cream. Out of the 30 students, what is the probability of a student enjoying ONLY chocolate or strawberry?

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About This Quiz & Worksheet

The addition rule of probability is a useful mathematical tool, as it covers multiple factors. This quiz will require you to remember facts about and apply the addition rule of probability.

Quiz & Worksheet Goals

This addition rule of probability quiz tests your ability to:

  • Determine the probability of something from a word problem using fractions
  • Find the probability asked of a word problem requiring percentages

Skills Practiced

  • Reading comprehension - ensure that you draw from the most important information found in the lesson on the addition rule of probability
  • Critical thinking - consider if the story problem involves mutually or non-mutually exclusive events in order to determine how to find the probability
  • Problem solving - calculate probability asked of given word problems in either fraction or percentage form

Additional Learning

The math lesson titled The Addition Rule of Probability: Definition, Examples, & Quiz meets the following learning objectives:

  • Explain the addition rule of probability
  • Contrast between mutually exclusive and non-mutually exclusive
  • Provide practice problems
  • List the steps to solve the aforementioned problems