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Worked example: Whole numbers on the number line

Created by Sal Khan.

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Video transcript

Where is 30 on the number line? So on the number line right over here, we see that as we go from 0, the first slash isn't 1. It's 3. So every slash here is going to go up by 3. So let's see if we can figure out where 30 is. So this is already marked as 3. Now this is going to be 3 more. It's 6, 9, 12, 15, 18, 21, 24, 27, 30. Another way you could have thought about it is if each of these marks are 3, to get to 30, we have to go to 10 of these marks. So you go 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Let's do a few more. Where is 24 on the number line? Well, once again, each of these marks is again 3. So it's going to be 3, 6, 9, 12, 15, 18, 21, and 24. Let's do one more. So now each mark is 4. So we're going to go 4, 8, 12, 16, 20. Another way you could think about it is if we're going up by 4, you have to go up 5 times to get up to 20. So this is 1, 2, 3, 4, 5. Either way, this should be the right answer.