In this lesson plan, your learner will practice adding and subtracting multiples of 10 by building on familiar single-digit addition and subtraction problems. We'll start with simple problems using objects and visual models to help your learner understand the basic principles. By comparing these single-digit problems to those involving tens, your learner will see the clear connection between adding and subtracting small numbers and larger multiples of ten.
Key Concepts for Adding and Subtracting Multiples of 10
The strategies used for adding and subtracting within 10 can be applied to multiples of ten. Here are some key strategies and how they extend to larger numbers:
Identifying Pairs that Make Ten: Recognizing pairs like 7 + 3 = 10 can be applied 70 + 30 = 100.
One More and One Less: Adding or subtracting one (5 + 1 = 6 or 7 - 1 = 6) can be applied to adding or subtracting ten (50 + 10 = 60 or 70 - 10 = 60).
Subtracting Consecutive Numbers: The difference between consecutive numbers is always one (9 - 8 = 1). Similarly, the difference between consecutive multiples of ten is always ten (90 - 80 = 10).
Using Doubles and Halves: Using patterns of doubles and halves, such as 4 + 4 = 8, can be used to solve 8 - 4 = 4. This can be extended to using 40 + 40 = 80 to solve 80 - 40 = 40.
Teaching Plan
The following activities will help your learner become confident with adding and subtracting multiples of 10. Be sure to work at a pace that is comfortable for your learner.
Examples and visuals to support the lesson:
1. Using Addition Strategies for Multiples of Ten
Begin with a familiar single-digit problem such as "three blue cubes plus two red cubes."
Have your learner represent the problem using objects, part-part-whole models (cherry or bar models), and equations. Then guide them in using complete sentences to describe what each number in the problem represents.
Next, present a similar problem, but this time involving tens. For example, three tens (30) of blue cubes and two tens (20) of red cubes.
Have your learner describe what they see and compare this problem to the previous one. Point out that in the previous problem, there were three ones and in this problem, there are three tens.
Similarly, for the other quantity, there were two ones in the previous problem, and in this one, there are two tens.
Represent the problem on a part-part-whole model and as an equation. For now, express the quantities as "three tens and two tens" rather than thirty and twenty.
Demonstrate the connection between this problem and the previous one. For example, since we know that three plus two is equal to five (3 + 2 = 5), then three tens plus two tens is equal to five tens (3 tens + 2 tens = 5 tens).
Provide additional practice problems and encourage your learner to describe the connection between adding single-digit numbers and adding units of ten.
Skill Check
I can use what I know about adding numbers under 10 to help me add multiples of 10.
2. Using Subtraction Strategies for Multiples of Ten
Next, explore subtraction of multiples of ten following the same process as adding multiples of ten.
Begin with a single-digit subtraction problem using concrete objects, part-part-whole models, and equations. Then present a similar problem using units of ten. Provide practice with a variety of objects and visual aids.
Continue to use stems sentences to link the calculation in units of ten with the single-digit calculation. For example, "I know that five minus two is equal to three, so five minus two tens is equal to three tens."
After practicing with several subtraction scenarios, have your learner complete missing number equations that involve adding and subtracting units of ten.
Skill Check
I can use what I know about subtracting numbers under 10 to help me subtract multiples of 10.
3. Developing Fluency with Multiples of Ten
Now, progress to using the proper names and numerals for the multiples of ten. Present your learner with a word problem using objects or pictures. Continue to reinforce the connection with single-digit calculations and multiples of ten.
Encourage your learner to represent the problem in different ways. For example, begin with single-digit equations like 3 boxes + 2 boxes = 5 boxes (3 + 2 = 5). Then, incorporate multiples of ten such as 3 tens + 2 tens = 5 tens (30 + 20 = 50).
Make sure that your learner can explain what each number in the equations represents in the context of the word problem.
You can use a variety of objects and visual aids to reinforce your learner's understanding including tens frames, base-ten number boards, place value counters, and part-part-whole models.
Provide missing number problems for your learner to practice. The goal is for your learner to solve the problems using their fluency in single-digit calculations rather than relying on objects and pictures.
Skill Check
I can use numbers under 10 to help me solve equations with multiples of 10.
4. Solving Word Problems with Multiples of Ten
Provide your learner with a range of practice problems without the corresponding single-digit calculations.
Include real-world scenarios, part-part-whole models, and equations.
When writing equations to represent the word problems, encourage your learner to describe the meaning of each number using full sentences.
Here are a few examples of real-world problems:
Ted has thirty cents and Sam has forty cents. How much do they have altogether?
The teacher buys sixty pencils. If twenty of them are red, and the rest are blue, how many blue pencils are there?
Sam has forty cents and her mom gives her another fifty cents. How much does she have now?
I have eighty centimeters of ribbon and use sixty centimeters of it to wrap a present. How much do I have left?
Skill Check
I can add and subtract multiples of ten to solve word problems.
Summary
This lesson plan will help your learner gain confidence in adding and subtracting multiples of ten by leveraging their understanding of single-digit calculations. By using a variety of methods such as objects, visual aids, and part-part-whole models, they will develop a strong conceptual foundation. The transition from single-digit addition and subtraction to working with tens will enhance their number sense and prepare them for future math challenges.
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Skill Check