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During this unit, students build on the work from Unit 3 as they practice and refine addition and subtraction strategies working with 3-digit numbers.
Math Words and Ideas
3- Tools to Represent Subtraction Problems
4- Adding and Subtracting Tens and Hundreds
5- Addition Strategies: Changing the Numbers
6- Tools to Represent Addition Problems
7- Adding More Than Two Numbers
8- Adding Strategies: Adding by Place
9- Addition Strategies: Adding One Number in Parts
Activities to Try at Home
Estimating and Making Change Look for opportunities to practice adding and subtracting with your child in stores and in restaurants.
When you and your child are buying something, figure out together what the change will be. For example, if you buy an item that costs $3.89 and give the clerk $5.00, figure out how much you should get back.
When you buy several things, ask your child to help you estimate how much all the items will cost. For example, if you buy three items that cost $4.95, $3.21, and $7.15, you might ask, “About how many dollars will these items cost?”
People do these problems in many different ways. Whenever these problems come up, encourage your child to figure out ways of estimating and making change, and share your ways of doing it.
Making Sense of Large Numbers With your child, look for large numbers in the newspaper, on packages, on signs, and around your home and neighborhood. Talk about the numbers. For example: “How much would this television cost if you get a $200 discount?”
How Did You Solve That? Ask your child to tell you about how he or she is adding and subtracting. Show that you are interested in these approaches. Because these strategies may be unfamiliar to you, listen carefully to your child’s explanation; you might even try using the new procedure to do a problem or two yourself. Let your child be the teacher! By explaining their thinking, students increase their understanding of addition and subtraction.
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