Students will learn how to relate repeated subtraction to division. Here's a decent video on this topic. However, in the video she uses Unifix cubes, which is not part of this lesson. Unifix cubes would be more appropriate for teaching division using equal groups, which is the topic directly preceding this one.
Division as Repeated Subtraction Using a Number Line by eHowEducation
Do these Khan Academy exercises:
Next, give your students this challenge:
Start Cube Drilling by NRICH
Conclude by leading this investigation:
3.OA.A.2: Interpret whole-number quotients of whole numbers, e.g., interpret 56 ÷ 8 as the number of objects in each share when 56 objects are partitioned equally into 8 shares, or as a number of shares when 56 objects are partitioned into equal shares of 8 objects each. For example, describe a context in which a number of shares or a number of groups can be expressed as 56 ÷ 8.