Worked example: Whole numbers on the number line
About this video
Sal finds whole numbers on number lines where each mark goes up by more than 1. With marks of 3 he skip-counts to 30 (10 marks) and 24 (8 marks), and with marks of 4 he skip-counts to 20 (5 marks).
You'll be able to
- find the size of each jump on a number line.
- skip-count to find a number on a number line.
- count how many jumps it takes to reach a number.
Key words
- number line
- A line with marks that show numbers in order.
- skip-count
- Counting by the same jump each time, like 3, 6, 9, 12.
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.
Video © Khan Academy, used under CC BY-NC-SA. Watch on Khan Academy. Puzzicle is not affiliated with Khan Academy.