Typo

[The Blade Dancer]

Module 3 Week 3 Day 12 Challenge Explanation Part 3

ii. Should say one vertex instead of two vertices

[debbie]

@The-Blade-Dancer Thanks so much for this comment. The wording of the second choice ii.) is actually correct because it is saying that there have to be two vertices the same color. Prof. Loh designated them to be the $\textcolor{pink}{\text{pink } X'\text{s}}$ in his diagram below:

We can try to avoid making two vertices the same color by visualizing that we are coloring the corners of the square one-by-one. The first one can be $\textcolor{red}{\text{red}}:$

The second one can be $\textcolor{orange}{\text{yellow}}:$

The third one can be $\textcolor{green}{\text{green}}:$

Now we are out of colors!

The fourth point must be either $\textcolor{red}{\text{red}}$, $\textcolor{orange}{\text{yellow}}$, $\text{ or } \textcolor{green}{\text{green}},$ so we are forced to have one pair of vertices the same color.

[The Blade Dancer]

@debbie