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### Unit 2: Lesson 1

Sal solves 0.822+5.65 using "standard algorithm".  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? • • in the equation, do you put 0.822 on the top or 5.65? its confusing... • 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!
•  • 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!
• • • • 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
———————— 