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Problem 278

Geometry Difficulty 1.5 Multiple choice CEMC Gauss (Grade 8) · Canada · 2014

The point $A(1,2)$ is reflected in the $y$ -axis.

The new coordinates are

Pick one

Official solution

The horizontal translation needed to get from Lori’s house to Alex’s house is the difference between the $x$ -coordinate of Lori’s house, 6, and the $x$ -coordinate of Alex’s house, $-2$ , or $6-(-2)=6+2=8$ .
The vertical translation needed to get from Lori’s house to Alex’s house is the difference between the $y$ -coordinate of Lori’s house, 3, and the $y$ -coordinate of Alex’s house, $-4$ , or $3-(-4)=3+4=7$ .

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From Lori’s house, Alex’s house is left and down.
Therefore the translation needed to get from Lori’s house to Alex’s house is 8 units left and 7 units down.

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