Lesson 6: Rounding to Thousandths

You probably remember that using rounded numbers makes working with numbers easier and helps with estimating answers. For example, if you're adding 578 and 712, you can round the addends (the numbers being added together) to the nearest hundred and then use the rounded sum to check your work: 600 + 700 = 1,300. That means your sum should be close to 1,300. In fact, when we add these numbers, the actual sum is 1,290, which is quite close to 1,300! If, however, you find a sum that isn't close to 1,300, then you will know that you need to add the numbers again because you've done something wrong.

In this lesson, you'll review rounding whole numbers and learn how to round decimal numbers.