To earn his knighthood, Radius embarks on a quest to rescue the imprisoned King Lell. In his adventures beyond the Mountains of Obtuse, the hero employs measurement skills to navigate a labyrinth of angles and solve cryptic geometric puzzles. The gift of a circular medallion (a protractor) proves invaluable as Radius realizes its ability to measure the angles. The inclusion of a circular medallion (protractor) allows students to interact with the story.--Ministry of Education website.

Mathematics grade 4 (2007). Mathematics grade 5 (2008). Mathematics grade 6 (2009).