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3rd grade math · Unit 2: Lines, shapes, area, and perimeter

Same area, different perimeters

What this lesson shows

Every rectangle of 12 square feet, and each perimeter.

The worked example

The lesson works this one step by step: 12. Then your kid tries one like it on paper.

The steps

  1. Same tiles, same area
  2. Try every rectangle
  3. Add the four sides
  4. Closest to a square: least

Helping at home

Find every way to make the number by multiplying two whole numbers, each 12 or less: each pair is a rectangle of tiles. The area is always the number of tiles. Add the four sides for each perimeter, and compare: the long, thin one has the most edge, and the one closest to a square has the least.

If your kid gets stuck

Try 2 rows, then 3 rows, and so on.

Watch it with Lux

With Lux, this lesson is a narrated video and a printed page your kid works on. Then Lux helps with the same math on their own worksheet, one question at a time.

See how Lux works

Standards

  • Common Core 3.MD.D.8
    Solve real world and mathematical problems involving perimeters of polygons, including finding the perimeter given the side lengths, finding an unknown side length, and exhibiting rectangles with the same perimeter and different areas or with the same area and different perimeters.
Matches standards in 50 statesSee each state's code

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