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Problem 37

Algebra Difficulty 1.1 Multiple choice CEMC Fermat · Canada · 2022

The average (mean) of two numbers is 7. One of the numbers is 5.
The other number is

Pick one

Official solution

Solution 1

Since the average of two numbers is 7, their sum is $2 \times 7 = 14$ .

Since one of the numbers is 5, the other is $14 - 5 = 9$ .

Solution 2

The average of two numbers is 7 and one of the numbers is 5.

Since 5 is 2 less than 7, the other number must be 2 more than 7, and so
is 9.

Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.