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2nd Grade · Math

Addition within 1,000: Regrouping Tens to Hundreds & Multiple Regrouping

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

Level Up Your Addition! 🚀

Hey Math Explorer! Have you ever played with building blocks? Imagine you have a big pile of single blocks (our "ones"), some sticks made of 10 blocks (our "tens"), and big flat squares made of 100 blocks (our "hundreds").

What happens when you collect 10 "ten" sticks? You can trade them for one big "hundred" flat, right? That’s exactly what we do in math! It’s called regrouping, and it’s a superpower that lets us add HUGE numbers!

From Pictures to Numbers

When we add numbers like 281 + 145, we start by looking at our blocks (or drawings of them!).

First, we add the ones.
Next, we add the tens. If we have 10 or more tens, we bundle them up and trade them for a new hundred! We "carry" that new hundred over to the hundreds place.
Finally, we add up all the hundreds, including any new one we just made.

This is how we solve problems with multiple regrouping, like when you need to regroup ones into tens AND tens into hundreds in the same problem. You're becoming a pro!

Key Takeaway!

When any column (ones, tens) gets too full with 10 or more, we bundle a group of 10 and move it over to the next bigger column on the left. It’s like leveling up your number!

Be a Math Detective: The Estimation Trick!

Now for a fun mission. A school collected 375 cans in the morning and 468 cans in the afternoon. How can we convince someone the total is over 800 without adding them up exactly?

We can use "friendly numbers" to estimate!
Think about it:

375 is a big number. It's more than 350.
468 is also a big number. It's more than 450.

What is 350 + 450? That's 800! Since our real numbers (375 and 468) are BOTH bigger than the friendly numbers we used, our final answer MUST be bigger than 800. Mission solved, detective!

Using estimation first helps us know if our final answer makes sense. Keep practicing, and you'll be an addition superstar!

Sample questions

1. If you have 2 hundreds blocks and 8 tens blocks, and you add 5 more tens blocks, how many blocks do you have in total after regrouping?

○ 230

○ 320

○ 340

✓ 330

Answer: 330 — Think about how many tens blocks make 1 hundreds block.

2. A baker made 340 cookies. Then he made 90 more cookies. How many cookies did he make in all?

✓ 430

○ 330

○ 440

○ 340

Answer: 430 — Add the tens first. If you have 10 or more tens, what do you do?

3. What is the sum of 165 and 178?

○ 243

✓ 343

○ 333

○ 323

Answer: 343 — Start by adding the ones. If you have 10 or more, regroup! Then add the tens, and then the hundreds.

Skills in this topic

Add two numbers with regrouping tens to hundreds using concrete base-ten blocks.
Represent addition with regrouping tens to hundreds using pictorial models.
Add two 3-digit numbers with multiple regrouping (ones to tens, tens to hundreds) using the standard algorithm.
Solve multi-step addition word problems within 1,000 involving multiple regrouping using bar models.
A school collected 375 cans in the morning and 468 cans in the afternoon. How can you convince someone that the total is over 800 cans without doing the exact calculation first?

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