Standard 4-5: The student will demonstrate through the mathematical processes an understanding of elapsed time; conversions within the U.S. Customary System; and accurate, efficient, and generalizable methods of determining area.

Lesson: This lesson has students explore areas of rectangular and irregular shapes on a grid to help them understand the concept of area and the units in which area is measured.

Lesson: Introduces students to modular (clock) arithmetic and how modular arithmetic can be used to encode messages using simple shift, multiple and affine ciphers.

Lesson: Students learn about perimeter and the units used to measure perimeter using a variety of materials including their hands, feet, rulers, and computer applets.

Activity: Learn the relationship between perimeter and area. A shape will be automatically generated with the perimeter that you choose. Calculate the area of this shape. Area Explorer is one of the Interactivate assessment explorers.

Activity: Calculate the area of a triangle drawn on a grid. Learn about areas of triangles and about the Cartesian coordinate system. Triangle Explorer is one of the Interactivate assessment explorers.