This lesson is designed to explain what regrouping is, why we regroup, and how to regroup.

We will learn how to add 2 and 3 digit addition problems using regrouping.

## Addition with Regrouping

You walk into a store, ready to spend your $30. You see the $15 game you’ve been wanting, but they also have a t-shirt that you really like for $18.

You really want to buy both, but do you have enough money? How can you figure it out? By adding, of course. First, set up your problem:

1 | 5 | |

+ | 1 | 8 |

= |

Now it is time to add the ones column. So, 5 + 8 = 13. But that is a two-digit number, so what do you do? Looks like it’s time to regroup.**Regrouping** is the process of carrying over values in excess of ten from one place value to another and is necessary whenever a group of ten or more is made.

Let’s think back to place values. You know that the first column to the right is the ones place, then the tens place, next the hundreds place and it continues on in that pattern. Regrouping becomes necessary if you make a group of ten or more in a single place value. Want a trick to remember this? If you have ten or more, add it next door.

## How to Regroup

As we just found out, if we add the numbers in the ones place, our number sentence is 5 + 8= 13, which gives us a group of ten: 10 + 3. And, since the number 13 is more than 10, we would need to regroup (don’t forget: ten or more, add it next door). The 3 would stay in the ones place and we would regroup or carry over our 1 ten to the tens place.

Next, you would add the numbers in the tens place, 1 + 1 = 2 plus the 1 we carried over from the ones place equals 3. So the answer is 3 tens and 3 ones or $30 + $3.

1 | ||
---|---|---|

1 | 5 | |

+ | 1 | 8 |

= | 3 | 3 |

The total cost of the game and the t-shirt is $33.

Do you have enough money? Unfortunately, the answer is no. Since $33 is more than $30, you do not have enough money to buy the game and the t-shirt. Being able to regroup helps us figure out when we have enough, when we need more, or when we have extra.

## Regrouping with 3 Digit Numbers

Adding 3 digit numbers follows the same pattern as adding 2 digit numbers. So let’s say you are adding 341 + 273. We always start adding in the ones place. 1 + 3 = 4. Since 4 is less than 10, there is nothing to regroup or carryover. Now we add the numbers in the tens place, 4 + 7 = 11.

The number 11 has 1 ten and 1 one or 10 + 1. So the 1 would stay in the tens place and we would regroup to carry the 10 over to the hundreds place. Finally, you’d add the numbers in the hundreds place, 3 + 2 = 5 plus the 1 that we carried over equals 6. So, 341 + 273 = 614.

1 | |||
---|---|---|---|

3 | 4 | 1 | |

+ | 2 | 7 | 3 |

= | 6 | 1 | 4 |

## Lesson Summary

**Regrouping** is the process of carrying over values from one place value to another and is done anytime there is a group of ten in a 2 or 3 digit problem. Always add your digits in the ones place first, then the tens place, and finally the hundreds place if you are adding 3 digit numbers. Regrouping helps you figure out if you have too much, just enough, or not enough of something.

Whenever you regroup just remember, ten or more add it next door!