enVision Mathematics Grade 3, Topic 8: Use Strategies and Properties to Add and Subtract
In this unit, your child adds and subtracts larger numbers using mental strategies built on place value. They break numbers into hundreds, tens, and ones, round to estimate, and use properties like changing the order of addends, the numbers being added. Two-step story problems put these strategies to work. Next, written methods for adding and subtracting within 1,000 take over.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Topic 8?
- Rounding to the nearest 10 or 100 on a number line, deciding whether 63 is closer to 60 or 70. Learn more: Rounding to the nearest 10 or 100
- Adding and subtracting in their heads by breaking numbers apart, such as 248 + 130 as 200 + 100, 40 + 30, and 8. Learn more about adding within 1,000: Adding within 1,000 · Learn more about subtracting within 1,000
- Using rounding to check two-step problems, so an estimate shows whether an exact answer is reasonable. Learn more: Story problems with two steps
Sample questions to try together
These are real questions from our practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
What is 43 rounded to the nearest 10?
- 50
- 40
- 30
How you can help
- Draw a quick number line on a napkin from 60 to 70 and ask your child where 63 and 68 land and which end each one is closer to.
- Ask your child to add two prices in their head, such as $2.45 and $1.38, by thinking of them as 245 and 138 cents ($3.83).
- Make up a two-step question on a walk, such as 125 steps to the corner and 90 more to the park, and ask how many steps the round trip takes (430).
Where kids can get stuck
- Changing the rounded digit but keeping the digits after it, so 347 rounded to the nearest ten becomes 357.
- Rounding every number ending in 5 down, unsure which way the halfway point goes, so 65 becomes 60.
- Losing track of pieces when breaking numbers apart, adding the hundreds and tens but leaving out the ones.
Practice makes perfect
Bobby's Math Club has practice problems that adapt to your child’s level, each with a detailed explanation and an easy-to-follow video, so your child can build confidence in these skills one step at a time.
Words your child will hear
- round
- To swap a number for the closest ten or hundred, like 47 to 50.
- estimate
- A number close to the exact answer that you find quickly.
- place value
- What a digit is worth based on its place, like the 4 in 347 meaning 4 tens.
- addend
- A number being added, like 6 and 8 in 6 + 8.
- sum
- The total you get when you add.
- difference
- How much more or less one number is than another.
- halfway
- The point exactly between two numbers, like 45 between 40 and 50.
- nearest ten
- The multiple of 10 closest to a number, like 50 for 47.
Ready to build your child’s confidence with mental math strategies?
In Bobby's Math Club, your child practices these skills at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free.
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Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
Which math standards does enVision Mathematics Grade 3 Topic 8 cover?
enVision Mathematics Grade 3 Topic 8 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
For teachers: Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence. Learn how Bobby's Math Club can help your students grow.