# Volumes of Cross-Sectional Solids (part 2 of 4)

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## Objective

SWBAT write variable expressions for areas of basic geometric shapes; SWBAT compute volumes of cross-sectional solids.

#### Big Idea

No matter how you slice it, finding volumes of cross-sectional solids is a blast! Today we continue with volumes of cross-sectional solids.

40 minutes

## Setting the Stage

10 minutes

The Bottle Project

Prior to continuing with cross-sectional solids, we first introduce the bottle project.  Distribute the Bottle project Description Sheet and centimeter graph paper, then briefly discuss how both solids of revolution and cross-sectional solids can be used to model many bottles and estimate their volumes.  Also note for students that a primary part of this project is in discussing possible sources of error (DO NOT SHOW TO STUDENTS) in students’ estimates, because for a variety of reasons students will not obtain the exact volumes as listed on the labels.  I usually make the project due sometime after two weekends have passed, but not the 3rd weekend; this allows students some flexibility in when they work on the project without making its due date too far away from our study of these topics.

Cross-Sectional Solids Examples Sheet

Distribute the Cross-Sectional Solids Examples Sheet, which like the Solids of Revolution sheet gives students several different examples integrating various cross-sectional shapes with respect to x and y.  Briefly discuss each example, observe that the same process was repeated in each example, and note how the pictures were sketched and labeled prior to setting up each integral.

Resources:  Bottle Project Description sheet, Cross-Sectional Solids Examples sheet

7 minutes

3 minutes