Rounding to the nearest 10 or 100
In 3rd grade, children learn to round whole numbers to the nearest 10 or 100, such as 347 to 350 or 300, using place value to decide which is closer.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
Try these with your child
These are real questions from our 3rd grade 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
Why this matters
Rounding gives your child a quick way to check their own answers, a habit that lasts for years. Knowing that 347 + 198 should be close to 350 + 200 helps them catch a total that comes out far too big or too small. Rounding stretches to thousands in 4th grade and to decimals in 5th, and it is handy in daily life, such as guessing a shopping total at the store.
Where kids can get stuck
- Looking at the wrong digit, such as checking the 7 when rounding 347 to the nearest hundred and getting 400.
- Changing the rounded digit but keeping the digits after it, so 347 rounded to the nearest ten becomes 357.
- Rounding every number that ends in 5 down, such as 65 to 60, unsure which way the halfway point goes.
How you can help
- Round prices at the grocery store together, such as asking whether a $38 toy is closer to $30 or $40, and use rounded prices to estimate the total.
- Round the car's distance or speed signs to the nearest ten as you drive, such as a sign saying 47 miles, and ask whether that is about 40 or 50.
- Draw a quick number line on a napkin from 60 to 70 and ask your child where 63 or 68 lands and which end each one is closer to.
If it’s helpful, you can sign up for free, adaptive practice in Bobby's Math Club.
Questions parents ask
Why does my child's school teach rounding with a number line?
A number line shows what rounding actually means: finding which friendly number is closest. When your child sees that 82 sits between 80 and 90 and is much nearer 80, the answer makes sense. Rhymes and rules can be helpful later, but children who learn them first often apply them to the wrong digit without noticing.
Why does 45 round up to 50 instead of down to 40?
45 is exactly the same distance from 40 and from 50, so there is no closest number. Mathematicians agreed to round up in that case so everyone gets the same answer. Your child does not need to discover this. It is a convention, and it is fine to tell them directly.
What is rounding used for?
Rounding helps your child estimate. Before adding 289 and 412, they might round to 300 and 400 and expect an answer near 700. If their exact answer is 1,201, they know to check their work. Adults round all the time with money, time, and distance, so it is a skill your child will use far beyond school.
Make learning math fun
Bobby's Math Club turns 3rd grade math practice into something fun to do together.
- Unlimited free practice
- Practice that starts where your child is and grows with them
- You see their progress and what to work on next
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.
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Join the clubNote for teachers: This skill is covered by Common Core math standard 3.NBT.A.1: “Use place value understanding to round whole numbers to the nearest 10 or 100.” Learn how Bobby's Math Club can help your students grow. (Common Core 3.NBT.1)