You will learn
- Add tens and ones separately.
- Bridge through a ten.
- Use a number line to add.
- Check that the sum is sensible.
Version 0.1 · published for early use · expert review pending Standards alignment: pending verification. Not yet reviewed against the Courseversity scorecard.
Student lesson
Words to know
The answer to an addition.
Break a number into tens and ones.
Jump to the next ten first.
A line with numbers in order.
1. Discover: two baskets
One basket has 34 oranges and another has 25. How many oranges are there in all?
2. Understand: adding within 100
Partition: 34 + 25: add the tens, 30 + 20 = 50, and the ones, 4 + 5 = 9. Then 50 + 9 = 59.
Bridge a ten: 47 + 36. Add the tens: 47 + 30 = 77. Then add the ones: 77 + 6 = 83. Or jump to 80 first (add 3), then add 3 more: 83.
A number line shows the jumps. Always check the sum is about the size you expect.
3. Explore: number line jumps
Draw a number line from 40 to 90.
- Start at 47.
- Jump +30 to 77.
- Jump +6 to 83.
- Check by adding 36 + 47.
Think about it: what did you notice?
47 + 36 = 83.
4. Practise
Guided practice
Question 1. 34 + 25?
30 + 20 = 50; 4 + 5 = 9; 59.
Question 2. 47 + 30?
77.
Question 3. 47 + 36?
77 + 6 = 83.
Independent practice
- 41 + 27
- 63 + 24
- 38 + 45
- 19 + 19
- 72 + 19
Answers are in the answer key below. Try first, then check.
5. Apply: everyday mathematics
A baker made 47 loaves in the morning and 36 in the afternoon. How many in all?
Show a sample answer
83 loaves.
6. Common mistake
Fix: Write each jump on a number line.
7. Check and master
Answer all questions. You will see feedback after each one.
Your result appears here after you answer every question.
8. Key takeaways
- Partition into tens and ones.
- Bridge to the next ten.
- Check with a number line.
9. Next lesson
Next lesson: Addition within 1,000. Keep going with the next idea in this course.
Printable worksheet
- 41 + 27
- 63 + 24
- 38 + 45
- 19 + 19
- 72 + 19
Homework
Add the ages of two people at home. Show how you added.
Answer key and marking scheme
| Question | Expected response | Marks |
|---|---|---|
| 41 + 27 | 68 | 2 |
| 63 + 24 | 87 | 2 |
| 38 + 45 | 83 | 2 |
| 19 + 19 | 38 | 2 |
| 72 + 19 | 91 | 2 |
| Total | 10 |
Practice answers: Worksheet: 1 68; 2 87; 3 83; 4 38; 5 91.
Quiz answers: 1 A, 2 B, 3 C, 4 A, 5 B, challenge C.
Mastery and remediation
| Objective | Bronze (Developing) | Silver (Proficient) | Gold (Advanced) |
|---|---|---|---|
| O1 Add tens and ones separately | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O2 Bridge through a ten | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O3 Use a number line to add | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
| O4 Check that the sum is sensible | Shows this with help from an adult or a picture | Does this independently and explains how they know | Explains it clearly and uses it in a new situation |
Proposed Courseversity thresholds for this page: Bronze = at least 3 of 5 core questions correct; Silver = all 5; Gold = all 5 plus the challenge. A badge is never a full record of progress.
If a learner struggles
- Find the misconception: Forgetting to add the tens that come from bridging. Write each jump on a number line.
- Explain another way: use real objects first, then pictures.
- Show a simpler example: Use bundles of ten and single sticks to add 34 + 25.
- Guided practice: work through one example together and let the learner try the next one.
- Reassess: use the quiz again or the worksheet.
- Move on when the learner shows Silver-level evidence independently.
Teacher package
1–5. Objectives, prerequisites, materials, preparation, duration
Lesson objectives. Learners will: add tens and ones separately; bridge through a ten; use a number line to add; check that the sum is sensible.
Prerequisite knowledge. Lesson 1; numbers to 100.
Materials. Counters (stones, seeds or bottle tops), paper, pencils, board or chalkboard. Low-resource options: use stones, seeds, sticks, bottle tops or drawings in the sand or on the board instead of printed materials.
Preparation. Gather the counters and draw the example pictures on the board before the lesson.
Suggested duration. 35–45 minutes.
6–9. Teaching procedure, explanation notes, guided and independent activities
Introduction (5 min). Start with the Discover situation and let learners suggest ideas before you teach.
Explanation (10 min). Teach the Understand section with real objects first, then pictures, then symbols and words.
Guided activity (10 min). Draw a number line from 40 to 90. Learners follow the Explore steps in pairs.
Independent activity (10 min). Learners complete the independent practice and the worksheet.
Assessment and reflection (5 min). Ask each learner to say one thing they learned and how they know it.
Teacher explanation notes. Use the concrete, pictorial, abstract order: real objects first, then pictures, then symbols and words. Return to real objects whenever a learner needs support.
10–12. Differentiation, formative assessment, common misconceptions
Support. Use real objects and work with a partner; say each step aloud together. Extension. Ask learners to make up their own example and explain it to a partner.
Formative assessment. Listen to learner explanations, ask “how do you know?”, and check the independent work.
Misconceptions. Forgetting to add the tens that come from bridging. Write each jump on a number line.
13–15. Assessment questions, answer keys, marking scheme
Use the quiz and worksheet on this page. The 10-mark scheme and all answers are in the answer key above. Re-check every answer and the marking scheme before publication.
16–19. Remediation, enrichment, homework, teacher reflection
Remediation. Use bundles of ten and single sticks to add 34 + 25. Enrichment. Invite learners to find or create three more examples at home or in the classroom and explain them. Homework. See above.
Teacher reflection. After teaching, record: which concepts learners understood; which misconceptions occurred; which activities worked; which learners need more practice; and what to improve next time.
Sources and standards
Alignment is pending verification and no external endorsement is claimed. Reference starting points named in the Courseversity standard: Common Core State Standards for Mathematics, Cambridge Primary and the IB Primary Years Programme. Specific standard codes will be added once checked against the official documents.