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## Middle school math (India)

### Course: Middle school math (India) > Unit 3

Lesson 2: Week 2- Intro to the number line
- Predecessors and successors
- Intro to whole numbers
- Natural numbers, whole numbers, Integers
- Adding 3-digit numbers
- Addition of 3 and 4 digit numbers
- Addition (word problems)
- Addition (word problems)
- Worked example: Subtracting 3-digit numbers (regrouping twice)
- Subtraction of 3 and 4 digit numbers

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# Intro to the number line

Let's look at how and why it is interesting to draw numbers as a line. Created by Aanand Srinivas.

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- but why cant we even write negative integers(4 votes)
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## Video transcript

if I say our food as a picture come to your mind and when I was in school the picture that came to my mind was this symbol that that I saw in books for four but I also thought of maybe four pencils or four razors or four elephants some something for four of something so I used to imagine it as four dots and if you had told me five then I might have imagined five as also maybe five dots this was my way of imagining this number picturing this number another way to do that is to arrange all of them from left to right starting from zero I go one two three four and I keep going and going and going and how far can I go I'll can go forever I'll never reach a place where I say oh this is the biggest number I'm never going to reach that so I'll go forever and you can see that these are all whole numbers this entire family because I start from zero and count forever these are whole numbers so what I'm really doing here is just arranging all these whole numbers in a line from left to right so I can just call this my line of numbers line of numbers so I have to make sure that I don't miss any number I can't just write 0 1 3 5 it's not like that I have to read all the numbers 0 1 2 so I have to keep doing plus 1 plus 1 plus 1 and keep writing as long as I don't miss any number and if I start from 0 then I get my line of whole numbers now this line of whole numbers is just what we call a number line now it might sound all big and new when you first hear it but this is all it is it is just a line of numbers so you draw it slightly differently we draw it like this just kind of paste it here so this is how you draw it but this is the same thing it starts from 0 this dot represents 0 it jumps plus 1 so if you just add 1 to 0 you'll get 1 and then plus 1 again you'll get 2 and this goes on now you can imagine your dots again over here if you want to 0 has no dots 1 has 1 dot 2 has 2 dots 3 will have 3 dots and so on so to say that it goes for we put a little arrow over here this arrow is to say that hey this does not stop with eight it goes on but I'm too lazy to draw all of it so this is just to say that so this what we have over here is what we call a number line and in this case because it has all the whole numbers we might call it a whole number line or a number line of whole numbers now one thing I want you to notice here is that as you go from left to right here you get bigger and bigger 1 2 3 and so on you'll keep getting bigger and bigger so right is always bigger than left I'm gonna write that over here right bigger than left so that's that's because of the way we have drawn it from left to right and one step will mean plus one one step to the right will mean plus one and one step to the left will mean minus one now you can do many things with this if you're wondering why this is useful you can imagine adding subtracting multiplying and all of it on this and as you play with the number line more you will see that it's it's quite a bit useful it's a quite a quite a useful way of imagining numbers