Subtracting within 1,000
In 2nd grade, children learn to subtract within 1,000 by taking hundreds from hundreds, tens from tens, and ones from ones; to break apart a ten or a hundred; and to check by adding.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
Try these with your child
These are real questions from our 2nd 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
A toy store had 450 toy cars and sold 120 of them. How many toy cars are left?
- 320
- 570
- 330
Why this matters
Subtracting bigger numbers lets your child answer real questions about distance, time, and money: how far is left, how many more, and how much change. Breaking a hundred into ten tens is the key idea. It sits behind every written method for subtracting larger numbers. Once your child sees why it works, numbers with zeros, like 500 - 238, become puzzles they can solve. And checking by adding is a habit that will serve them every year.
If trading tens and hundreds is still new, your child can review adding within 1,000, which uses the same trades in the other direction.
Where kids can get stuck
- Taking the top digit from the bottom one when the top is smaller, so 402 - 175 becomes 373.
- Checking by adding the two starting numbers, 402 + 175, instead of adding the answer back to 175.
- Breaking apart a ten but forgetting to lower the tens digit, so 352 - 128 comes out as 234 instead of 224.
How you can help
- Find how far is left on a long drive. If the trip is 412 miles and you've gone 175, have your child count up: 25 to reach 200, 200 more to 400, then 12 more. That's 237.
- Count down to a goal. If your child's class wants 250 cans for the food drive and has 168, ask how many more are needed, then check by adding the answer back to 168.
- Pick two house numbers on a walk, like 418 and 395, and ask how far apart they are. Talk about whether taking away or counting up felt easier.
If it’s helpful, you can watch the kid-friendly video below, or sign up for free, adaptive practice in Bobby's Math Club.
Kid-friendly explanation
Questions parents ask
Why is my child learning to subtract by breaking apart tens and hundreds?
Breaking a hundred into ten tens, or a ten into ten ones, is what lets your child subtract when a place doesn't have enough. Adults may call it borrowing. Showing it with blocks or a drawing makes the trade visible, so the written steps make sense instead of feeling like magic. Later, the same trade is written as crossing out a digit and writing a smaller one.
Why are problems with zeros, like 500 - 238, so hard?
With 500 - 238, there are no tens or ones to take from, so your child must break a hundred into ten tens, then break one of those tens into ten ones. That's two trades before any subtracting. Showing it step by step helps. Some children find counting up from 238 easier: 2 to reach 240, 60 to reach 300, and 200 to reach 500, which makes 262.
My child adds three-digit numbers well but makes mistakes subtracting. Why?
Subtracting has more steps where a slip can happen. Your child has to notice when a place needs a trade, break a ten or hundred apart, and keep track of what changed. Before starting, encourage your child to look at each place and say whether it has enough. That one pause catches many mistakes before they happen.
Make learning math fun
Bobby's Math Club turns 2nd grade math practice into something fun to do together.
- Free, unlimited practice for every child in your family
- A few minutes a day, at just the right level
- 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 2.NBT.B.7: “Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.” Learn how Bobby's Math Club can help your students grow. (Common Core 2.NBT.7)