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Sal adds 7 + 6 using the number line. Created by Sal Khan.

## Want to join the conversation?

• Why are number lines used? Isn't the adding or taking objects away thing easier than a number line?
• You will need to know numbers lines later on, when you start geometry with points, lines, curves and vectors.
Also, numbers lines can be more useful than objects when it comes to:
* Negative numbers
* Large numbers (think thousands)
* Decimal numbers (1.623, 76.8).
* Skip counting
• Hey, I'm curious to know if someone wants to answer my question.
Can someone tell me all the possibilities (of additions) to make 13?
• There are infinite possibilities because you can add negitive numbers to positive numbers. For example, 15+(-2) is 13.
• The number line is infinite. What does "infinite" mean? Is it complete?
• Here is an interesting piece of entomology, study of words. Finite means ending. In, as a prefix means not. So infinite means not ending.
• so when ever you add a even nuber and a odd number you will get a odd?
• Yes.

Even+Even=Even (6+8=14)
Odd+Even=Odd (6+5=11)
Odd+Odd=Even (3+7=10)
• Is there an easier and quicker way to work it out? If there is then you should edit the video. I know the other ways are quick but what if you have to answer it instantly?

Kindly Regards
Emma Winstanley
• If you know what 7+7 is, than all you need to do is subtract one. Since 7+7 = 14, 7+6 = 13. (That is the easiest way to answer it fast besides memorizing it)
• Would it still work as "6 + 7"?
• Yes! There is this one law for adding numbers, which is called the Commutative Law.

This Commutative Law states that
When we add or multiply two numbers then the resultant value remains the same, even if we change the position of the two numbers. Or we can say, the order in which we add or multiply any two real numbers does not change the result.

In short, a + b = b + a.

If we have more terms, let's say
a + b + c, does it equal to b + a + c?

We can consider a + b first
Since a + b = b + a, we get
b + a + c, which is what we wanted!
• how do you do expanded form on one-digit numbers?
(1 vote)
• Whatever one-digit number you choose, will already be in its expanded form.
• I still have trouble adding 7 + 6. Any more tips?
• Well, you can start with the basics of adding the numbers that are relative together (6+6) then add the remainders. Particularly, an easier equation will help in solving the your main problem.

(6+6) = ?
? + 1 = [The Solution]
(1 vote)
• Is it the same to add bigger numbers like hundreds or higher? Or does what you do change?
(1 vote)
• Coleman Vaughn,
Yes. its all the same.