Library / /212 of 428

, 2026

Geometry Difficulty 1.2 Junior Find the answer Canada

Quadrilateral $RSTU$ is formed by placing two equilateral triangles together, as shown.The measure of $\angle RST$ is

Pick one

Solution

The measure of each of the three angles in an equilateral
triangle is $\dfrac{180\degree}{3}=60\degree$ . Thus, $\$\angle RSU=\angle TSU=60\degree$ $. Since$ $\angle RST=\angle RSU+\angle$
TSU $, then the measure of$ $\angle RST=60\degree+60\degree=120\degree\$.$

Figure for this problem

Want a route through all this instead of an archive? The track puts 2,604 problems in a working order, from Junior Challenge level to the IMO shortlist.

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