If you’ve been playing Hogwarts Legacy for any lengthy of time, you have probably run into one of the above puzzle doors with triangles and numbers and symbols on them.

They often identify them solely based on their resemblance to prototypes: e.g., a shape will be called a triangle if it looks like an equilateral triangle with a horizontal base – all others are ...

As a basic modeling requirement, students should be able to identify common shapes, such as circles, rectangles, squares and triangles, and angles, as in acute, obtuse and right.

A version of this article appears in print on Aug. 27, 2019, Section D, Page 3 of the New York edition with the headline: How Many Triangles? Count on Math to Help.