### Video Transcript

Which of these numbers should be written in the box? 814, 836, 831, 820, or 825.

Here, we have a number line showing spaces between 814 and 836. What should go in the box? The first option is 814, but 814 is already on the number line. Next 836 and again 836 already has a space on the number line. We would not fill in the box with a number that’s already on the number line.

From there, we have three options. Something that can help us make this decision is finding what is in the middle between 814 and 836. How many units are between 814 and 836? We do subtraction: 836 minus 814 equals 22. If the total distance equals 22, then each half equals 11 because 11 plus 11 equals 22.

To find out what goes right in the middle, we’ll add 11 to 814. 814 plus 11 equals 825. The halfway point on this number line is 825. We found where 825 goes and it’s not in the box. We can now say that whatever is going in the box must fall between 825 and 836.

Out of our two remaining options, only one of these falls between 825 and 836. 831 is larger than 825 and smaller than 836 and it fits in the box.