Go Math! Grade 5, Chapter 3: Add and Subtract Decimals
In this unit, your child reads, writes, and compares decimals to thousandths, rounds them, and then adds and subtracts them using place value and estimation. Race times and prices on a receipt make good practice, since lining up the decimal points is the key habit. After the division unit, this opens the decimal part of the year, which continues with multiplying decimals.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Chapter 3?
- Reading and writing thousandths, like 2.305 as two and three hundred five thousandths, and comparing decimals by place value. Learn more about reading and writing decimals to thousandths: Reading and writing decimals to thousandths · Learn more about comparing decimals to thousandths
- Rounding decimals to the nearest whole number, tenth, or hundredth, like 2.97 to 3.0, to check sums and differences. Learn more: Rounding decimals, like 4.68 to 4.7
- Adding and subtracting decimals to hundredths, regrouping across the decimal point when needed, like 5.3 − 2.48 = 2.82. 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
Which number is greater than 1.5?
- 1.500
- 1.52
- 1.499
How you can help
- Look at results from a swim meet or race, like 25.43 and 25.4 seconds. Ask your child who won and by how much, 0.03 seconds.
- Hand your child a short shopping list with prices, like $3.29, $4.50, and $1.85. Ask them to round to the nearest dollar for an estimate, then add exactly, $9.64.
- Pay with a $10 bill for something costing $6.37 and ask your child to count up the change, $3.63, then check by subtracting.
Where kids can get stuck
- Reading 2.305 as “two point three hundred five” and losing the meaning of the thousandths.
- Rounding 2.97 to the nearest tenth as 2.10, unsure how to carry over to 3.0.
- Lining up the last digits instead of the decimal points, so 5.3 − 2.48 is set up wrong.
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, like 0.5 or 2.37, showing parts of a whole.
- thousandth
- One of 1,000 equal parts of a whole, written 0.001.
- expanded form
- Breaking a number apart by place value, like 400 + 20 + 1.
- compare
- To look at two numbers and tell which is larger.
- round
- To change a number to a nearby, simpler one, like 4.68 to 4.7.
- decimal point
- The dot that separates the whole number from the parts smaller than one.
- regroup
- To trade 10 of one place for 1 of the next place, like 10 ones for 1 ten.
Ready to build your child’s confidence with decimals to thousandths?
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 Go Math! Grade 5 Chapter 3 cover?
Go Math! Grade 5 Chapter 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.