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Adding decimals is a breeze when you follow these simple steps: First, line up the decimal points and write the numbers one below the other. Next, start adding from the smallest place value (thousandths) and carry over any extra value to the next place if needed. Finally, include the decimal point in your answer. Mastering decimal addition helps build strong math skills for everyday life.

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Created by Sal Khan.

## Want to join the conversation?

• Why do you put the smallest decimal on top and the longest decimal on the bottom?
• It doesn't matter which decimal value is longer or shorter to write, or which comes first or second…

In the video Sal arranged the higher valued decimal on top, (he placed the value with 5-whole over the 0-whole), and says it is just his preference, and it would add the same either way.
because…

Addition is Commutative, (able to be rearranged and still add the same).
2 + 5 = 7
5 + 2 = 7

★We can have either decimal value on top or bottom, but…

★ We must LINE UP THE DECIMALS to keep each place value aligned throughout the calculation.

0.822 + 5.65 = ?

``  0.822+ 5.65————————  6.472 ←same answer  5.65+ 0.822————————  6.472 ←same answer``

Use the decimals to guide the place value alignment: line up the decimals above and below, then add each column of numbers, empty spaces are equal to zero.

(ㆁωㆁ) Hope this helps someone!
• hi
can you divide the ten by the two hundred
• yes bc it will turn out to be 2000 thing for asking
• Hey, what if you had 9.78 - 3.2? What would I do with the 8?
• You would do 9.78-3.20 which would be 6.58
• in the equation, do you put 0.822 on the top or 5.65? its confusing...
• 5.65 on top and then you put a 0 after the 5 and then you put the 0.822 and add
• It doesn't matter which decimal value is longer or shorter to write, or which comes first or second…

In the video Sal arranged the higher valued decimal on top, (he placed the value with 5-whole over the 0-whole), and says it is just his preference, and it would add the same either way.
because…

★ Addition is Commutative, (able to be rearranged and still add the same).
2 + 5 = 7
5 + 2 = 7

★We can have either decimal value on top or bottom, but…

★ We must LINE UP THE DECIMALS to keep each place value aligned throughout the calculation.

0.822 + 5.65 = ?

0.822
+ 5.65
————————

5.65
+ 0.822
————————

★Use the decimals to guide the place value alignment: line up the decimals above and below, then add each column of numbers, empty spaces are equal to zero.

(ㆁωㆁ) Hope this helps someone!
• When exactly the "standard algorithm" happens in this solution?
• To use the standard algorithm, follow these steps in order:

Line up the decimal points

``   36.413   12.5+  30.08------------``

Fill in the blank spots with zeros

``   36.413   12.500+  30.080------------``

Add, beginning with the smallest place first

thousandths: 3+0+0=3
hundredths: 1+0+8=9
tenths: 4+5+0=9
ones: 6+2+0=8
tens: 3+1+3=7

Be sure to drop the decimal down into the answer

``   36.413   12.500+  30.080------------   78.993``

Hope this helps!
• are there questions on these or not?