The Mean
Part of the Expressions & Data section of Coddy's Pre-Algebra journey. Lesson 27 of 52.
Three friends go fishing and catch 3, 5 and 10 fish. If they pooled the catch and shared it out equally, how many would each one take home? Altogether they caught 18, and 18 shared among 3 is 6. That fair-share number is the mean, the most common kind of average.
To find a mean, add all the values, then divide by how many values there are: (3 + 5 + 10) / 3 is 18/3, which is 6. On the board the total sits on top of a fraction bar with the count underneath, so you finish the top first and divide last.
Why divide by the count? The total is shared out evenly, one share per value. That is also why the mean does not have to be one of the values: nobody caught exactly 6 fish, yet 6 is each friend's fair share.
Challenge
Four friends score 4, 8, 6 and 10 points in a game. The board shows their total over the count, (4 + 8 + 6 + 10) / 4. Work out the mean score, one step per line.
Try it yourself
Simplify the expression
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Expressions & Data
1Variables and Expressions
What a Variable IsWriting ExpressionsExpressions from StoriesTwo OperationsRecap: Expressions2Evaluating Expressions
Substituting a ValueNegative InputsPowers in ExpressionsFormulasRecap: Evaluating5Patterns and Sequences
Continuing a PatternThe Common DifferenceThe nth TermWriting the RuleRecap: Sequences3The Distributive Property
Number PropertiesMental MathDistributing LettersDistributing a MinusRecap: Distributing