Answer key: Area of rectangles (Grade 8)
Companion answer key for the printable worksheet "Area of rectangles (Grade 8)" — Common Core CCSS.MATH.8.G.A.1, Advanced difficulty. Use it to spot-check during the lesson or grade afterward.
Sample answers
| # | Question type | Sample answer |
|---|---|---|
| 1 | 22 + 48 | 70 |
| 2 | 28 + 30 | 58 |
| 3 | 44 + 45 | 89 |
| 4 | 12 + 35 | 47 |
| 5 | 34 + 46 | 80 |
| 6 | 35 + 43 | 78 |
| 7 | 34 + 48 | 82 |
| 8 | 13 + 2 | 15 |
How to grade this worksheet
This answer key is intentionally short — eight items or fewer — so you can spot-check during the lesson rather than waiting until the end. For Math worksheets at the advanced level, we recommend the following grading flow.
- Pencil-only spot check. Walk by every five minutes and circle (lightly) any item that looks off. Do not announce the score.
- Self-grade. When the student finishes, hand them this answer key and let them grade their own work in pen. Self-grading produces about 30% better retention than parent-grading at this age.
- Two-question debrief. Pick the two items they missed and ask: "Walk me through what you tried." Their explanation usually reveals whether it was a careless error or a genuine concept gap.
- Log the score. Note the score, the date, and the standard code (
CCSS.MATH.8.G.A.1) in your portfolio. Three data points across a month is enough to know if the standard is mastered.
If the student misses more than half of the items, do not reteach the same way. Switch modalities — manipulatives, a drawn diagram, a verbal walk-through — and revisit a fresh worksheet on the same standard the next morning.