Main content

### Course: 2nd grade > Unit 4

Lesson 1: Visually adding within 1,000# Adding and subtracting within 1,000: FAQ

Frequently asked questions about adding and subtracting within 1,000.

## Why do we need to learn how to add and subtract within $\mathrm{1,000}$ ?

Adding and subtracting within $\mathrm{1,000}$ is important because it is the foundation for more complex math skills. We use these skills every day, whether we're counting change at the store, measuring ingredients in a recipe, or figuring out how much time we have left in a day.

## How can we use number lines to help us add and subtract within $\mathrm{1,000}$ ?

There are a few different ways we can use a number line to help with addition and subtraction within $\mathrm{1,000}$ :

- We can start at one of the numbers we're adding or subtracting, and count up or down from there. For example, if we want to add
, we could start at$97+548$ on the number line and count up$548$ places to reach the sum of$97$ .$645$ - We can use the number line to break a larger problem into smaller chunks. For example, if we want to subtract
from$248$ , we can break that down into subtracting$560$ , then$200$ , then$40$ , using the number line to keep track of where you are each step of the way.$8$

## How can we use place value blocks to help us add and subtract within $\mathrm{1,000}$ ?

Place value blocks can be really helpful when we're trying to add or subtract within $\mathrm{1,000}$ . When we're adding, we can use the blocks to visualize the numbers we're combining.

When we're subtracting, we can use the blocks to help us "take away" part of a number. For example, if we want to subtract $278$ from $842$ , we can use the blocks to see that we need to take away two hundreds, seven tens, and eight ones from eight hundreds, four tens, and two ones. Once we take away the blocks we don't need, we're left with five hundreds, six tens, and four ones-- or $564$ .

No matter what kind of math problem we're trying to solve, place value blocks can be a great tool to help us understand what's going on.

## How do we add up to four $2$ -digit numbers?

We can add up to four $2$ -digit numbers the same way we would add any other numbers. We start by adding the first two numbers together to get a sum. Then, we add the third number to that sum, and finally add the fourth number. It can be helpful to line the numbers up so that the place values match.

## How can we use what we will learn in this unit in the real world?

There are countless ways we use addition and subtraction in our everyday lives! For example, we might need to add up the cost of multiple items we want to buy, or subtract money we spend from our total budget.

## Want to join the conversation?

- how can we add 23+99 on a numberline(4 votes)
- Notice 99 = 100 - 1. Notice 23 = 20 + 3.

So you can rewrite the equation as (20 + 100) + (-1 + 3)

Start from 20, then add 100 to 120. Last subtract one to 119, and add 3 to 122.(12 votes)