Mean Math Example 4

Follow the full solution, then compare it with the other examples linked below.

Example 4

medium
Five quiz scores have a mean of 1818. Four of the scores are 1212, 1717, 2020, and 1919. What is the fifth score?

Solution

  1. 1
    A mean of 1818 across 55 scores means the total must be 5×18=905 \times 18 = 90.
  2. 2
    Add the known scores: 12+17+20+19=6812 + 17 + 20 + 19 = 68.
  3. 3
    The missing score is 90−68=2290 - 68 = 22.

Answer

Fifth score=22\text{Fifth score} = 22
Reverse-mean problems work by finding the required total first, then subtracting the known values. This avoids recomputing the average from scratch.

About Mean

The arithmetic mean (average) of a data set is the sum of all values divided by the number of values.

Learn more about Mean →

More Mean Examples

Example 1 easy

Find the arithmetic mean of the data set: [formula].

Example 2 medium

A student scored [formula], and [formula] on five tests. What score does she need on the sixth test

Example 3 easy

Find the mean of [formula].

← All Mean Examples Mean Concept