Grade 3 · lesson 2 of 4

Add Areas of Non-Overlapping Parts

Use the supplied non-overlapping rectangular parts.

About 20 minutes, plus any extended practice

Download the grade pack

Supplied materials

  • Paper and a pencil; drawing and spoken explanations are welcome. An adult may read directions and options aloud.
  • Supplied worked-case record: An L-region is split into a 3×5 rectangle and an adjoining 2×4 rectangle with no overlap.
  • All quantities and shape descriptions are supplied in the worked example and questions; no purchase or personal information is needed.

Learn the idea

A composite region can be split into rectangles whose interiors do not overlap. Find each area and add them to count the whole. Shared boundary segments have no area, but an actual overlapped patch would be counted twice. The partition should cover all of the target region.

Use the supplied non-overlapping rectangular parts. Calculate each product, add their areas, and label the combined result in square units. Explain why the non-overlap statement makes direct addition valid.

Check that the stated parts cover the region completely. Do not add overlapped areas without correcting the double count. Draw the two rectangular parts with distinct patterns and their shared boundary marked.

  1. Draw the two rectangular parts with distinct patterns and their shared boundary marked.
  2. Follow the worked example. Point to each number or shape feature and say what it tells you.
  3. Use the supplied non-overlapping rectangular parts.
  4. Try the question and then the three practice questions. Check your answers and explain any change you make.
Worked example

See the method in action

An L-region is split into a 3×5 rectangle and an adjoining 2×4 rectangle with no overlap. Their areas are fifteen and eight square units, totaling 23. The shared boundary does not add another square-unit region; only the two stated interiors are counted. Check that the stated parts cover the region completely. Do not add overlapped areas without correcting the double count. Draw the two rectangular parts with distinct patterns and their shared boundary marked.

Your turn

Check your reasoning

Your answer is temporary and is not saved to an account. Download your current answer before leaving or reloading. Written work on paper or in another app stays in your own file.

Helpful tips
  • Check that the stated parts cover the region completely.
  • Do not add overlapped areas without correcting the double count.
A region has non-overlapping rectangular parts 2×4 and 2×3 units. What is its total area?

Feedback appears here after you check. This is practice, not a graded school assessment.

See the answer and explanation

14

Find each part’s area and add because the interiors do not overlap. The result is 14.

Take it further

Parts 4×6 and 3×2 with no overlap have total area 30 square units.

Nothing here is saved to an account or sent to a teacher. The answer download includes your current choice and any checked feedback. It does not include choices from the separate More practice section. Download that section separately.

More practice: try new cases

Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.

More practice: try new cases
1. A region has non-overlapping rectangular parts 3×4 and 2×3 units. What is its total area?
Need a hint?
  • Check that the stated parts cover the region completely.
  • Do not add overlapped areas without correcting the double count.
2. A region has non-overlapping rectangular parts 4×4 and 2×3 units. What is its total area?
Need a hint?
  • Check that the stated parts cover the region completely.
  • Do not add overlapped areas without correcting the double count.
3. A region has non-overlapping rectangular parts 5×4 and 2×3 units. What is its total area?
Need a hint?
  • Check that the stated parts cover the region completely.
  • Do not add overlapped areas without correcting the double count.

Your choices are temporary. Feedback appears after you check all the answers.

Nothing here is saved to an account or sent to a teacher. Keep your own notes or download them before leaving. The score describes these questions; it does not certify subject mastery.

Check the subject sources

These LifeStarter passages, scenarios and exercises are authored for this Academy with AI assistance and review. External resources keep their publishers’ terms. A grade label suggests a starting level; it does not establish alignment with your school’s complete requirements.