This math topic focuses on teaching students how to measure lengths in millimeters using a centimeter ruler. It involves a practical application of measurement skills, specifically centered on understanding and interpreting metric units. Each question requires measuring the length of a crayon depicted in an image, and the students must choose the correct measurement from a set of options. This exercise is part of a broader introduction to metric units in measurement, aiming to build foundational skills in using metric system tools like rulers for precise measurements.