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Algebra Difficulty 1.3 Junior Find the answer Canada

The average of $15$ integers
is $18$ . The average of $5$ of these integers is $12$ . What is the average of the other
$10$ integers?

Pick one

Solution

Since $15$ integers have an
average of $18$ , then the sum of
these $15$ integers is $15\times18=270$ .

Since $5$ of these integers have an
average of $12$ , then the sum of
these $5$ integers is $5\times12=60$ .

Thus the sum of the other $10$
integers is $270-60=210$ , and so
their average is $\dfrac{210}{10}=21$ .

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