4th Grade Math Lesson

Seating by Design: Factors, Multiples, and Prime vs. Composite

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4th GradeBTC Vertical Whiteboard FramingCCSS.4.OA.B.450 min

Learning Objective

Students will find all factor pairs for whole numbers 1–100 using systematic array models, distinguish factors from multiples, and classify numbers as prime or composite (CCSS.4.OA.B.4).

Lesson Overview

Students work in random groups of 3 at vertical whiteboards to discover factor pairs through rectangular seating array models for a community theater, progressing from simple arrays up to 100 seats, then classifying numbers as prime or composite.

Materials

Vertical whiteboards or large chart paper taped to walls
Dry-erase markers (multiple colors per group)
Erasers or paper towels
Random grouping cards (pre-made)
Printed Four-Quadrant Note Sheets (one per student)
Pencils

Scaffolded Task Progression

1Task 1

The theater has 12 seats to arrange. At your whiteboard, draw every possible rectangular array (rows × columns) for 12 seats. Label each array with its factor pair. How many different rectangles can you find?

[ Interactive graph / diagram — available in the full lesson ]

2Task 2

The theater now has 18 seats. Using the same systematic method (start at

1

and work up), find all factor pairs for

18

. Draw each rectangular array on your board and label it. How many unique factor pairs are there?

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