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CEMC Gauss (Grade 8), 2023

Geometry Difficulty 1.5 Junior Find the answer Canada

Bindu’s bike tires have a radius of 30 cm. She rides her bike far
enough that the tires rotate exactly five times. How far does Bindu’s
bike travel?

Pick one

Solution

The given list, $2,9,4,n,2n$
contains 5 numbers.

The average of these 5 numbers is 6, and so the sum of the 5 numbers is
$5\times 6=30$ .

That is, $2+9+4+n+2n=30$ or $15+3n=30$ , and so $3n=15$ or $n=5$ .

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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.