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Problem 274

Geometry Difficulty 1.5 Multiple choice CEMC Gauss (Grade 8) · Canada · 2013

A cube has a surface area of 54 cm $^{2}$ . The volume of the cube, in cm $^{3}$ , is

Pick one

Official solution

Substituting $x=4$ into $3x+2y$ we get, $3(4)+2y=12+2y$ .

Since this expression $12+2y$ is equal to 30, then $2y$ must equal $30-12$ or 18.
If $2y=18$ , then $y$ is $18\div2$ or 9.

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