Main content

## Arithmetic (all content)

### Unit 3: Lesson 1

Multiplication intro- Multiplication as equal groups
- Intro to multiplication
- Basic multiplication
- Multiplication with arrays
- Understand multiplication using groups of objects
- Multiply with arrays
- Worked example: Whole numbers on the number line
- Represent multiplication on the number line
- More ways to multiply
- Ways to represent multiplication

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# Worked example: Whole numbers on the number line

Created by Sal Khan.

## Want to join the conversation?

- How can i learn my multipication facts/time tabels in a creative way?(4 votes)
- just use your drawling and make a time table and use like stars or things u love to drawl(0 votes)

- you can learn a lot of things in Kahn.(2 votes)
- It was his sole purpose when he had his epiphany.(2 votes)

- who created the number line and how(2 votes)
- John Wallis

The number line was created by John Wallis (1616-1703), an English mathematician that was investigating negative numbers during his time period. He had created this line to represent negative numbers in a simple manner.(2 votes)

- ummmm how do u do like times like big numders(2 votes)
- why is he on the number line one we are working on?(2 votes)
- Even with the video I'm still struggling. Does anyone have an easier way of doing this?(1 vote)
- Can anybody help me sometime idont get it im new to it?(1 vote)
- I'll help you out. Just ask me some questions and i'll show you how to figure them out.(1 vote)

- What is a good way to do mental multiplication and division with big numbers?? I know all my times tables and all, but I'm not good at mental multiplication.(1 vote)
- There tends to be a feasible limit for most people on how large a number you can do in your head. Typically it's about how many of the extra steps you can keep in your head at a time and recall while doing it. If you mean doing it at all, just do more practice on multiplication and division, practice helps develop doing it in your head even if your still doing it on paper or computer scratch pad. Try doing one of the steps in your head without using the paper and work on increasing it. In short even if it says you have mastered the concept, that just means you understand what it is not that you can't improve your ability to do multiplication and division, in which case just do more exercises, over and over again until your satisfied with your ability in it.(1 vote)

- The question is so easy because the answer on the numberline is not that hard(1 vote)
- What is 91/100 as a decimal?(1 vote)
- Decimals are infinite. 91 out of 100 is 0.91(1 vote)

## 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.