Mathematics · Primary 1 · Numbers and Operations · Semester 1

Addition within 20

Students will add numbers with sums up to 20, building on number bonds and using the make-ten strategy.

• MOE Syllabus Outcomes
• MOE: N(iii).3
• MOE: N(iii).4

About This Topic

Addition within 20 helps Primary 1 students develop mental math fluency by combining single-digit numbers and teen numbers. They build on number bonds to decompose numbers into parts that make sense, such as seeing 15 as 10 and 5. The make-ten strategy becomes key: students learn to reach 10 first, then add the rest, like 9 + 6 as (9 + 1) + 5 = 15. They also explore adding a single-digit to teens, such as 13 + 4, and practice checking sums through inverse operations or counting objects.

This topic fits into the Numbers and Operations unit in Semester 1, aligning with MOE standards N(iii).3 and N(iii).4 for basic addition facts. It strengthens number sense, prepares for multi-digit addition, and connects to real-life contexts like sharing toys or counting fruits. Students gain confidence in flexible strategies over rote counting.

Active learning suits this topic well. Manipulatives like counters or ten-frames make strategies visible and interactive. Games encourage repeated practice in a fun way, while partner checks build collaboration and error detection skills. These methods turn abstract bonds into concrete experiences, boosting retention and enthusiasm for math.

Key Questions

1. How does the make-ten strategy help us add numbers beyond 10?
2. What happens when we add a single-digit number to a teen number?
3. How can we check if our addition is correct?

Learning Objectives

• Calculate the sum of two single-digit numbers and a teen number, with sums up to 20, using the make-ten strategy.
• Explain how decomposing numbers into parts helps in adding numbers greater than 10.
• Demonstrate the make-ten strategy by visually representing addition problems with ten-frames or number bonds.
• Compare the results of adding single-digit numbers to teen numbers using different strategies, such as counting on or using number bonds.

Before You Start

Number Bonds to 10

Why: Students need a strong understanding of how numbers up to 10 can be combined to make 10 to effectively use the make-ten strategy.

Counting and Cardinality

Why: Students must be able to count reliably and understand that the last number counted represents the total quantity.

Key Vocabulary

Make-ten strategy	A method for adding numbers where you first make a ten from one of the numbers, then add the remaining amount.
Number bond	A visual representation showing how a whole number can be broken down into two or more parts.
Teen number	Any whole number from 11 to 19, which is composed of one ten and some additional ones.
Decompose	To break a number down into smaller parts, such as breaking 7 into 5 and 2.

Watch Out for These Misconceptions

Common Misconception

Always count all fingers from 1 without strategy.

What to Teach Instead

Students often rely on slow finger counting for 8 + 7. Introduce make-ten with ten-frames to show faster paths. Pair discussions reveal why strategies beat counting, building flexible thinking through shared examples.

Common Misconception

13 + 4 is 17 because 3 + 4 = 7.

What to Teach Instead

They ignore the ten, treating teens as single digits. Use base-ten blocks to model tens and ones clearly. Group activities with visuals help students see the structure, correcting via hands-on rebuilding.

Common Misconception

No need to check answers.

What to Teach Instead

Students assume sums are correct without verification. Teach inverse subtraction with counters. Partner checks in games encourage explaining methods, catching errors collaboratively.

Active Learning Ideas

Simulation Game: Make-Ten Pairs

Pair students and give each a set of number cards from 1 to 10. Players take turns drawing two cards and using counters to make ten, discarding pairs that work and drawing again if not. First to empty hand wins. Discuss strategies used after each round.

25 min·Pairs

Hands-on: Ten-Frame Addition

Provide ten-frames and counters to small groups. Students build teen numbers first, then add single-digits by filling frames. Record sums on mini-whiteboards and check by removing counters. Rotate materials every 5 minutes.

30 min·Small Groups

Stations Rotation: Number Bond Hunt

Set up stations with dice, linking cubes, and bond cards. Roll dice, build bonds to 20, snap cubes into tens and ones. Write equations and verify with peers. Groups rotate stations.

35 min·Small Groups

Whole Class: Addition Bingo

Distribute bingo cards with sums to 20. Call out problems using make-ten; students mark answers. First bingo shares strategy. Review all problems as class.

20 min·Whole Class

Real-World Connections

• A baker adding sprinkles to a cake might need to calculate if they have enough, for example, adding 8 sprinkles to a cake that already has 12. They can use the make-ten strategy to quickly find the total.
• When counting toys, a child might have 9 cars and receive 5 more. They can use the make-ten strategy to figure out they now have 14 cars in total.

Assessment Ideas

Exit Ticket

Provide students with an addition problem, such as 8 + 5. Ask them to write down the steps they used to solve it, specifically showing how they used the make-ten strategy. They should also write the final sum.

Quick Check

Present students with a series of addition problems on a whiteboard, like 7 + 6 and 13 + 4. Ask students to hold up fingers or use mini whiteboards to show the first step of their make-ten strategy for each problem.

Discussion Prompt

Ask students: 'How is using a number bond to add 9 + 4 similar to using the make-ten strategy? How is it different?' Encourage them to explain their thinking using examples.

Frequently Asked Questions

How to teach the make-ten strategy for addition within 20?

Start with ten-frames or counters to show partners to 10, like 8 + 2 first for 8 + 7. Practice with visuals: draw bonds or use linking cubes. Progress to mental math through timed partner games. Reinforce with daily warm-ups linking to key questions like adding beyond 10. This builds fluency aligned to MOE standards.

What are common errors when adding to teen numbers?

Pupils may forget the ten in 14 + 3, saying 7. Or add digits separately without regrouping. Address with concrete tools like straws bundled in tens. Small group stations let them manipulate and discuss, linking to number bonds for correction.

How can active learning help with addition within 20?

Active methods like games and manipulatives make strategies tangible: ten-frames visualize bonds, bingo builds speed. Pairs or groups promote talking through steps, correcting errors on the spot. This matches Primary 1 needs, turning practice into play while hitting MOE goals for fluency and checking.

Ways to check addition sums up to 20?

Use inverse: subtract from total to verify parts. Or recount objects used. Nearpod or worksheets with self-check boxes work well. In class, partner verification with counters ensures understanding. Ties to key question on accuracy, fostering independence.