39 . Using the Average to Find the Sum
Sum = (Average) × (Number of terms)If the average of 10 numbers is 50, then they add up to 10 × 50, or 500.
40 . Finding the Missing Number
To find a missing number when you’re given the average, use the sum. If
the average of 4 numbers is 7, then the sum of those 4 numbers is 4 × 7, or
- Suppose that 3 of the numbers are 3, 5, and 8. These 3 numbers add up
to 16 of that 28, which leaves 12 for the fourth number.
41 . Median and Mode
The median of a set of numbers is the value that falls in the middle of the
set. If you have 5 test scores and they are 88, 86, 57, 94, and 73, you must
first list the scores in increasing or decreasing order: 57, 73, 86, 88, 94.
The median is the middle number, or 86. If there is an even number of
values in a set (6 test scores, for instance), simply take the average of the
two middle numbers.
The mode of a set of numbers is the value that appears most often. If your
test scores were 88, 57, 68, 85, 99, 93, 93, 84, and 81, the mode of the scores
would be 93 because it appears more often than any other score. If there is
a tie for the most common value in a set, the set has more than one mode.