Lesson 9-5: Similar Objects

Investigating Geometry: Surface Area and Volume

Henrico County Public Schools

Lesson 9-5: Similar Objects

Click and drag the mouse over either prism to rotate the object.

Objective:

SOL G.14: The student will use similar geometric objects in two- or three-dimensions to
a) compare ratios between side lengths, perimeters, areas, and volumes;
b) determine how changes in one or more dimensions of an object affect area and/or volume of the object;
c) determine how changes in area and/or volume of an object affect one or more dimensions of the object; and
d) solve real-world problems about similar geometric objects.

Other Web Sites

Glencoe: On Line Quiz
Understanding Ratios of Areas in Inscribed Figures Explore the relationship between the area of a triangle and the area of a second triangle whose vertices are the midpoints of the sides of the first triangle.

Puzzle & Problems

A store sells balls of yarn in two different sizes. The diameter of the larger ball is twice the diameter of the smaller ball. If the balls of yarn cost $7.50 and $1.50, respectively, which ball of yarn is the better buy?
Hint: compute the ratio of volumes and the ratio of costs, then compare the ratios to see which is the better buy?