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Problem 239

Geometry Difficulty 1.4 Multiple choice CEMC Cayley · Canada · 2022

An equilateral triangle is made of cardboard and lies on a table.
Paola stands in front of the table and sees the triangle in the position
shown.

She flips the triangle over, keeping edge $QR$ on the table throughout the flip. From this position, Paola then flips the triangle again, this time keeping edge $PR$ on the table throughout the
flip. What is the resulting position of the triangle that Paola
sees?

Pick one

Official solution

Starting with [[IMAGE0]] and flipping across $QR$ results in [[IMAGE1]] .

Now flipping across $PR$ results
in [[IMAGE2]] , which is the resulting position that Paola sees.

Figure for this problem

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