Math Expressions Grade 5, Unit 2: Addition and Subtraction with Decimals
In this unit, your child connects fractions to decimals, seeing tenths, hundredths, and thousandths as places in a number. They compare and round decimals, learn that each place is worth ten times the place to its right, and add and subtract decimals by lining up place values. It builds on the fraction unit before it and leads into multiplying and dividing fractions.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 2?
- Recognizing that a digit is worth ten times as much one place to the left, so 0.7 is ten times 0.07. Learn more: What each digit is worth, including decimals
- Reading, writing, and comparing decimals to the thousandths, knowing that 0.5 is greater than 0.48. 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 a given place, including tricky cases like 2.97 to the nearest tenth, which is 3.0. Learn more: Rounding decimals, like 4.68 to 4.7
- Adding and subtracting decimals to the hundredths, lining up place values and estimating to check each answer. 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
How many hundredths are in 1 tenth?
- 10
- 1/10
- 100
How you can help
- Add two prices at the store, like $2.39 and $4.75, on paper or out loud. Then check your child's total against the receipt together.
- Compare race times from a sports broadcast, like 52.4 seconds and 52.38 seconds. Ask which is faster and by how much.
- Round the price of each item in your cart to the nearest dollar, then add the rounded amounts for a quick estimate of the total.
Where kids can get stuck
- Thinking more digits means a bigger number, so 0.35 seems greater than 0.4.
- Stumbling when rounding carries over, writing 2.10 or 2.9 for 2.97 rounded to the nearest tenth.
- Lining up the last digits instead of the decimal points, so 4.5 + 2.36 comes out as 2.81 instead of 6.86.
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.
- thousandth
- One of 1,000 equal parts of a whole, written 0.001.
- place value
- The value a digit has because of its place in a number.
- compare
- To decide which number is greater, less, or whether they are equal.
- round
- To change a number to a nearby, easier number, like 4.68 to 4.7.
- decimal point
- The dot that separates the whole number from the parts of a whole.
- estimate
- A close guess found by rounding or using easy numbers.
Ready to build your child’s confidence with adding and subtracting decimals?
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 Math Expressions Grade 5 Unit 2 cover?
Math Expressions Grade 5 Unit 2 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.