Unknown Numbers Assessment
Math Progress Numbers Within 1,000
Finding the Unknown
Name:
Date:
Strategies you can use:
• Base-Ten Sketches (□ | .) • Open Number Line • Expanded Form / Place Value
1 Find the Missing Number
346 + ? = 782
Show your model or place value strategy:
Answer:
2 Story Problem
Maya had 215 beads. Her friend gave her some more beads. Now Maya has 540 beads in all. How many beads did her friend give her?
Show your model or place value strategy:
Answer: beads
3 Find the Missing Number
? − 164 = 358
Show your model or place value strategy:
Answer:
4 Story Problem
A store had some mystery books. They sold 187 books today. Now there are 245 books left. How many mystery books were there at first?
Show your model or place value strategy:
Answer: books
5 Find the Missing Number
620 − ? = 274
Show your model or place value strategy:
Answer:
6 Story Problem
The school wants to collect 800 canned goods. The students have collected 463 cans so far. How many more cans are needed?
Show your model or place value strategy:
Answer: cans
Check your work:
I drew a model or used place value I wrote my answer on the line
Goal Score: ___ / 6
Unknown Numbers Answer Key
Teacher Reference Master Key & IEP Rubric
Unknown Numbers Answer Key
Standard / Goal Equations & Word Problems to 1,000
Target Mastery 5 of 6 (83%+)
IEP Goal Target: Student represents & solves for the unknown in any position using models/place value. Award 1 pt for accurate model + 1 pt for correct answer
1 346 + ? = 782 Answer: 436
Exemplar Strategy (Inverse / Number Line):
\( 782 - 346 = \mathbf{436} \). Student jumps on number line from 346 to 746 (+400), to 780 (+34), to 782 (+2) = 436.
LD Error Alert: Student adds \( 346 + 782 = 1,128 \), missing that the unknown is an addend.
2 215 + ? = 540 beads Answer: 325 beads
Exemplar Strategy (Part-Part-Whole):
Whole = 540; Known Part = 215. \( 540 - 215 = \mathbf{325} \). Or base-ten blocks: subtract 2 hundreds, 1 ten, 5 ones (with regrouping).
LD Error Alert: Student forgets to rename 4 tens to 3 tens when regrouping for \( 0 - 5 \) ones (resulting in 335).
3 ? − 164 = 358 Answer: 522
Exemplar Strategy (Unknown Minuend / Total):
Combine parts: \( 358 + 164 = \mathbf{522} \). Expanded: \( 300+100=400 \); \( 50+60=110 \); \( 8+4=12 \). Total = 522.
LD Error Alert: Student sees minus sign and subtracts \( 358 - 164 = 194 \). Check if student recognizes the missing start.
4 ? − 187 = 245 books Answer: 432 books
Exemplar Strategy (Bar Model):
Start = Sold (187) + Left (245). \( 187 + 245 = \mathbf{432} \). Base-ten sketch combining 3 flats, 12 rods, 12 units = 4 flats, 3 rods, 2 units.
LD Error Alert: Student subtracts \( 245 - 187 = 58 \). Prompt: "Did they have more books before selling or fewer?"
5 620 − ? = 274 Answer: 346
Exemplar Strategy (Counting Up on Number Line):
Count up from 274 to 620: \( +6 \rightarrow 280 \), \( +20 \rightarrow 300 \), \( +320 \rightarrow 620 \). Jumps: \( 6 + 20 + 320 = \mathbf{346} \).
LD Error Alert: Regrouping across zero errors during vertical subtraction \( 620 - 274 \) (often writing 454).
6 463 + ? = 800 cans Answer: 337 cans
Exemplar Strategy (Make Next Hundred):
\( 463 + 7 = 470 \); \( 470 + 30 = 500 \); \( 500 + 300 = 800 \). Total added: \( 300 + 30 + 7 = \mathbf{337} \) cans.
LD Error Alert: Subtracting smaller digit from larger digit incorrectly: \( 800 - 463 \rightarrow 463 \) or \( 447 \).
IEP Progress Monitoring Record Sheet Student: ____________________ Date: ________
1. Modeling / Representation
Drew sketches, number lines, or place value charts.
Score: ___ / 6 pts
2. Computation Accuracy
Correct numerical value for the unknown.
Score: ___ / 6 pts
3. Overall Goal Mastery
Mastered (80%+) Progressing
