Reveal Math Grade 5, Unit 3: Addition and Subtraction of Decimals
In this unit, your child rounds decimals to estimate, then adds and subtracts decimals to the hundredths. They line up digits by place value, use models and estimates to check answers, and solve problems with money and measurements. It builds directly on the place-value unit before it and leads into multiplying whole numbers.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 3?
- Rounding decimals to the nearest whole number, tenth, or hundredth to make quick estimates before adding or subtracting. Learn more: Rounding decimals, like 4.68 to 4.7
- Adding and subtracting decimals to the hundredths with models and place value, regrouping across the decimal point when needed. Learn more about adding and subtracting decimals to hundredths: Adding and subtracting decimals to hundredths · Learn more about multiplying decimals to hundredths · Learn more about dividing decimals to hundredths
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
Amara swam one length of the pool in 18.6 seconds. What is her time to the nearest whole second?
- 20 seconds
- 18 seconds
- 19 seconds
How you can help
- Estimate a grocery bill by rounding each price to the nearest dollar as items go in the cart. Compare your estimate with the real total.
- Count back change together after a purchase, like paying $10 for something that costs $6.35. Ask your child to subtract to find the change.
- Compare two distances on a walk or ride, like 1.6 miles and 0.85 miles. Ask how much longer one is, rounding first to estimate.
Where kids can get stuck
- Looking at every digit to the right when rounding, so 3.149 gets rounded up to 3.2 instead of 3.1.
- Subtracting the smaller digit from the larger in each column, so 4.3 − 1.75 ends up as 3.45 instead of 2.55.
- Lining up the right-hand digits instead of the decimal points, so 7.5 + 2.25 comes out as 3.00 instead of 9.75.
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
- decimal
- A number with a decimal point, showing parts of a whole in tenths, hundredths, and smaller.
- tenth
- One of 10 equal parts of a whole, written 0.1.
- hundredth
- One of 100 equal parts of a whole, written 0.01.
- round
- To change a number to a nearby, easier number, like 4.68 to 4.7.
- estimate
- A close guess found by rounding or using easy numbers.
- decimal point
- The dot that separates the whole number from the parts of a whole.
- regroup
- To trade 10 of one place for 1 of the next place, or the reverse.
Ready to build your child’s confidence with decimal addition and subtraction?
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 Reveal Math Grade 5 Unit 3 cover?
Reveal Math Grade 5 Unit 3 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.