Answer key: Adding 10ths and 100ths

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 medium level, we recommend the following grading flow.

1. Pencil-only spot check. Walk by every five minutes and circle (lightly) any item that looks off. Do not announce the score.
2. 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.
3. 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.
4. Log the score. Note the score, the date, and the standard code (CCSS.MATH.4.NF.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.