Answer key: Subtracting within 100 (Grade 8) · Grade 8 Math

#	Question type	Sample answer
1	158 − 113	45
2	49 − 17	32
3	152 − 112	40
4	50 − 19	31
5	153 − 37	116
6	47 − 35	12
7	108 − 10	98
8	57 − 32	25

Question type

Sample answer

158 − 113

49 − 17

152 − 112

50 − 19

153 − 37

116

47 − 35

108 − 10

57 − 32

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.OA.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.

Sample answers

How to grade this worksheet