Grade 1 Mathematics Weeks 33–34: Teacher Guide and Answer Key
For adults: model the worked example before independent practice, verify each of the four responses, and ask students to explain their reasoning. Adapt pacing and reteach with fresh numbers. Do not show these keys before students finish.
Week 33: Mixed operation fluency within 20
Day 161: Add and subtract within twenty
Teaching focus: Use counting on, counting back, or a ten-frame for single-step calculations.
Model separately: 4 + 7 = 11; start at 7 and count on four.
Practice 1: 6 + 8 = ___ Answer: 14.
Practice 2: 15 − 7 = ___ Answer: 8.
Practice 3: 9 + 5 = ___ Answer: 14.
Practice 4: 17 − 6 = ___ Answer: 11.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Day 162: Use a make-ten strategy
Teaching focus: Complete ten before adding the rest. Explain the two steps of the addition.
Model separately: 9 + 6 = 10 + 5 = 15.
Practice 1: 8 + 7 = ___; explain how to make ten. Answer: 15.
Practice 2: 9 + 4 = ___; show the ten first. Answer: 13.
Practice 3: 7 + 6 = ___; break an addend to make ten. Answer: 13.
Practice 4: 6 + 5 = ___; show your ten-frame steps. Answer: 11.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Day 163: Use related facts
Teaching focus: Addition can check subtraction, and subtraction can check an addition fact.
Model separately: 13 − 5 = 8 because 8 + 5 = 13.
Practice 1: If 8 + 6 = 14, then 14 − 8 = ___ Answer: 6.
Practice 2: If 7 + 5 = 12, then 12 − 5 = ___ Answer: 7.
Practice 3: Which addition fact checks 16 − 9 = 7? Answer: 7 + 9 = 16.
Practice 4: Which subtraction fact checks 6 + 8 = 14? Answer: 14 − 6 = 8 or 14 − 8 = 6.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Day 164: Choose the operation in a story
Teaching focus: Listen for what changes, not just a clue word. Draw the story before choosing addition or subtraction.
Model separately: There are 12 pencils; 4 are taken. 12 − 4 = 8.
Practice 1: There were 14 marbles; 6 were lost. How many remain? Answer: 8.
Practice 2: Nine shells plus 8 shells makes how many? Answer: 17.
Practice 3: A basket has 12 apples, and 5 are eaten. How many are left? Answer: 7.
Practice 4: Seven birds land near 8 birds. How many birds now? Answer: 15.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Day 165: Review mixed facts independently
Teaching focus: Solve addition and subtraction without copying a model. Use two strategies to check one response.
Model separately: 13 − 4 = 9; 9 + 4 = 13.
Practice 1: 11 + 7 = ___ Answer: 18.
Practice 2: 18 − 9 = ___ Answer: 9.
Practice 3: □ + 6 = 15 Answer: 9.
Practice 4: A child has 16 counters and gives away 7. How many remain? Answer: 9.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Week 34: Explain mathematical reasoning
Day 166: Explain how you added
Teaching focus: Show a picture or number line to explain a sum. The explanation should match the numbers.
Model separately: 6 + 5 = 11 by starting at 6 and counting five more.
Practice 1: Show with a picture how 6 + 7 = ___. Answer: 13.
Practice 2: Use a number line to add 8 + 5. Answer: 13.
Practice 3: Explain a make-ten way to add 9 + 6. Answer: 15.
Practice 4: Draw counters for 4 + 8 and find the total. Answer: 12.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Day 167: Explain how you subtracted
Teaching focus: Model the start, what is removed, and the amount remaining.
Model separately: 15 − 6 = 9 because taking away 6 from 15 leaves 9.
Practice 1: Explain how taking away 5 from 14 leaves ___. Answer: 9.
Practice 2: Draw a model for 16 − 8. Answer: 8.
Practice 3: Show counting back for 12 − 7. Answer: 5.
Practice 4: Use addition to check 15 − 9. Answer: 6.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Day 168: Find and fix a mistake
Teaching focus: Check an incorrect calculation using counters, a ten-frame or an inverse fact.
Model separately: A claim that 8 + 5 = 12 is incorrect; the total is 13.
Practice 1: A student says 7 + 5 = 11. Correct the sum. Answer: No; 12.
Practice 2: A student says 16 − 8 = 9. Fix the result. Answer: No; 8.
Practice 3: A student says 6 + 7 = 13. Is it correct? Answer: Yes.
Practice 4: A student says 18 − 9 = 8. Fix it. Answer: No; 9.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Day 169: Compare two methods
Teaching focus: Two correct approaches can give the same answer. Explain why both represent the same quantity.
Model separately: 7 + 8 is 15 by counting on or making ten.
Practice 1: Compare counting on and making ten for 8 + 5. What is the total? Answer: 13.
Practice 2: Show two ways to check 14 − 6. Answer: 8.
Practice 3: Find 7 + 9 using two strategies. Answer: 16.
Practice 4: Explain why 11 − 4 and 5 + 2 have the same result. Answer: 7.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.
Day 170: Defend a conclusion
Teaching focus: Use a number sentence, drawing, and a short explanation. Say what evidence proves the answer.
Model separately: Ten less than 63 is 53 because one ten is removed.
Practice 1: Explain why 54 + 10 is 64. Answer: One ten is added; ones stay 4.
Practice 2: Explain why 80 − 20 is 60. Answer: Two tens are removed; six tens remain.
Practice 3: Use a drawing to prove 13 − 5 = 8. Answer: A correct 13-item model with 5 removed.
Practice 4: Why is 62 greater than 58? Answer: Six tens exceed five tens.
Scoring: one point per correct response (4 total). Accept mathematically equivalent explanations or drawings; document support given and reteach errors using new examples.