Subtracting Numbers with Regrouping in Ones and Tens

Free sample questions, a clear explanation, and 5 practice skills with an AI tutor that guides without giving the answer away.

Unlocking Your Subtraction Superpowers!

Hey, Math Explorer! Have you ever tried to share your crayons with a friend, but you only have a full box of 10 and a few loose ones? If your friend needs more crayons than you have loose, what do you do? You open the box, of course! You trade one big box for 10 single crayons.

In math, we do the exact same thing! It's a superpower called regrouping. Sometimes, when we subtract, we don't have enough ones. So, we trade one ten for 10 ones. It’s like opening a box of crayons to get the job done!

From Blocks to Drawings

Remember using your base-ten blocks? If you have 4 tens rods and 2 ones cubes (that's 42) and need to subtract 5, you can't take 5 ones away from 2 ones. So, you trade one tens rod for 10 ones cubes. Now you have 3 tens and 12 ones. Easy peasy! 12 - 5 is 7. The answer is 37.

We can also be math artists and draw this! In a place value chart, if we need more ones, we just cross out a ten and draw 10 new ones in the ones column. It's the same cool trick, just on paper!

Key Takeaway!

When the number on the bottom is bigger, go next door and get ten more!

Let's Solve a Library Mystery!

A library has 342 books. If 128 books are checked out, how many are left? Let's use regrouping to find out!

Look at the Ones: We need to do 2 - 8. We can't! So, we go to the tens place. We trade one ten from the 4 tens. The 4 becomes a 3, and our 2 ones becomes 12 ones. Now, 12 - 8 = 4.
Look at the Tens: We now have 3 tens left. We need to subtract 2 tens. 3 - 2 = 1. We can do that!
Look at the Hundreds: Finally, we look at the hundreds place. 3 - 1 = 2. Awesome!

So, 342 - 128 = 214. There are 214 books left!

You did it! You are an amazing regrouping rockstar! Keep practicing your new superpower.

Sample questions

1. You have 3 tens and 4 ones (34). You want to take away 6 ones. What should you do first with your base-ten blocks?

○ Take away 6 ones from the 4 ones.

✓ Break 1 ten block into 10 ones blocks.

○ Add 6 ones blocks to the 4 ones blocks.

○ Take away 3 tens blocks.

Answer: Break 1 ten block into 10 ones blocks. — Think about how to get more ones when you don't have enough.

2. Maya has 2 tens and 1 one (21) using base-ten blocks. She needs to subtract 4. After she breaks 1 ten block into 10 ones, how many tens and ones does she have?

○ 2 tens and 11 ones

○ 1 ten and 10 ones

✓ 1 ten and 11 ones

○ 0 tens and 21 ones

Answer: 1 ten and 11 ones — Remember to add the new ones to the ones you already have.

3. Look at the base-ten blocks. You have 4 tens and 2 ones (42). You need to subtract 7. Which option shows the blocks *after* you regroup 1 ten?

✓ 3 tens and 12 ones

○ 4 tens and 12 ones

○ 3 tens and 2 ones

○ 4 tens and 7 ones

Answer: 3 tens and 12 ones — When you regroup a ten, you lose a ten block and gain ten ones blocks.

Skills in this topic

Subtract a 1-digit number from a 2-digit number with regrouping in the ones place using base-ten blocks (Concrete)
Subtract a 2-digit number from a 2-digit number with regrouping in the ones place using place value charts (Pictorial)
Subtract a 2-digit number from a 3-digit number with regrouping in the ones and/or tens place
Subtract two 3-digit numbers with regrouping in the ones and/or tens place
A library has 342 books. If 128 books are checked out, explain how you would use regrouping to find how many books are left

Practice 50+ questions on this topic

Unlimited interactive practice, progress tracking, and Nova — your AI tutor. Free to start.

Start learning free →