In this culminating lesson, students apply and integrate many concepts and skills from the past three units to estimate and calculate various quantities in a home improvement context.

In the Warm-up, students notice and wonder about features of the four walls of a bedroom. This is followed by an activity in which students calculate the paintable area of the walls. This activity is marked optional because area calculation is not the focus of the current unit. Next, students estimate the amount of paint needed to cover the walls and then compute the associated costs. In the final activity, students find the amount of time necessary to paint all the walls given information about the rate of painting.

Along the way, students reason about areas of two-dimensional figures, solve problems involving ratios and rates, and work with percentages. Though there is a single measurement for the total wall area to be painted, the amount of paint needed will depend on some assumptions and decisions that students make about the work involved. As students apply the mathematics that they know and make assumptions to solve real-world problems, they engage in aspects of mathematical modeling (MP4).

Depending on instructional choices made, this lesson could take one or more class meetings. For instance, more time would be needed if students calculate the wall area (rather than using a given area), research paint costs and deals in local stores, or create a display for sharing their solutions.