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Problem 245

Geometry Difficulty 1.4 Multiple choice CEMC Gauss (Grade 7) · Canada · 2024

The length of a rectangle is twice its width. The perimeter of
the rectangle is $120$ cm.
The width of the rectangle is

Pick one

Official solution

The perimeter of a rectangle is made up of two widths and two
lengths.

Since each length is twice the width, then two lengths is equivalent to
four widths, and so the perimeter is equal to $2+4=6$ times the width.

Since the perimeter of the rectangle is $120 \text{ cm}$ , then the width of the rectangle is $\frac{120\text{ cm}}{6}=20 \text{ cm}$ .

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