The Being Complementary Game gives kids a chance to work with a protractor to determine the measures of two complementary angles. One thing that will become immediately apparent as they play this game is that there are a lot of different ways to divide up a right angle into two angles.The measures of the complementary angles they create by drawing those lines will vary quite a bit. This game gives kids the opportunity to practice measuring with a protractor so that their final angle measurements are more precise.

Most kids have quite a bit of trouble learning to read the measurements when using a protractor so this game provides a fun, non-intimidating way for them to learn that skill. After all, their finished measurements must add up to 90 degrees otherwise there is a problem. Once they get more skilled with the protractor, dividing the right angle into three pieces will give them more precision practice.

The addition of the toss of the die to determine the points can alter the game quite quickly. And planned strategies can backfire here. You could divide up the angle into an 80-degree angle and a 10-degree angle hoping that your opponent will be scored on the 10-degree angle. But one toss of the die will mean that the 10-degree angle you planned for your opponent turns out being your score instead! Plan to listen to a lot of moaning and groaning when someone who is close to winning gets an unfortunate toss of the die.

The Adaptation that suggested playing the game with supplementary angles is a great idea too. Kids sometimes get complementary and supplementary angles confused but by playing this game in different rounds the distinction between the two types of angles will stick with them.

Common Core Mathematical Standards 4.G Draw and identify lines and angles, and classify shapes by properties of their lines and angles.

Common Core Mathematical Practices
6. Attend to precision.