Worked examples
Two examples
Example 1
Ana’s first 3 scores are 80, 75 and 90. What must she score on the next test to have a mean of 85?
- A mean of 85 over 4 tests is a total of 85 × 4 = 340.
- She has 245. 340 − 245.
Answer: 95
Example 2
Four numbers have a mean of 10. Three of them are 8, 12 and 9. What is the fourth?
- The total must be 40. 8 + 12 + 9 = 29.
- 40 − 29.
Answer: 11
Where this is taught: Quiz 28: Mean, Median, Mode, and Range, “The mean: the fair share”
The drill
Ten problems
How many:
Type each answer, then press Check my answers at the bottom. Commas in large numbers are fine.Write each answer on the line. The answer key, with the reasoning, is on the last page.