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Adding three decimals

Adding decimals is easy when you follow these steps: line up the decimal points, fill in any missing digits with zeros, and then add the numbers from the smallest place value to the largest. By following this method, you can accurately add decimals and solve real-world problems. Created by Sal Khan and Monterey Institute for Technology and Education.

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Video transcript

We need to add 7.056 to 605.7 to 5.67. Now when you're adding any number, you always want to make sure you line up numbers in the same place. And especially when you're dealing with decimals, the easiest way to do that is to just line up the decimals. So let's do that. So the first number right here is 7.056. This second number right here is 605.7. And then this last number is 5.67. So now we have everything lined up. Everything that's in the ones place is below or above everything else in the ones place. Everything in the tenths place is below or above everything else in the tenths place, and so on and so forth. So we can add. So let's add it. So you want to start off in the smallest place. So you start off here. This is the tenths, hundredths, thousandths place. This is literally 6 thousandths, and you want to add it to the other thousandths. There aren't any other thousandths. So you can view it two ways. You can just bring in this 6 down, or you could view this 605.7 as the same thing as 605.700. You can add as many zeroes to the right of this decimal, to the right of the 7, as you want, since we're sitting on the right side of the decimal, without changing its value. You can also do it here. This 5.67, you can write it as 5.670. When you write it like this, and you have 6 plus 0 plus 0 is 6. And you keep going. 5 plus 0 plus 7 is 12. You write the 2 in the hundredths place, and carry the 1. 1 plus 0 plus 7 is 8, plus 6 is 14. Write the 4, regroup the 1 into the ones place. 1 plus 7 is 8. 8 plus 5 is 13. 13 plus 5 is 18. This is 18. Carry or regroup the 1. 1 plus 0 is just 1. And then finally. You have the 6 in the hundreds place. Nothing gets added to it, so you can just bring down that 6 and it's right there. And you don't want to forget the decimal. And so when you add the numbers you get 618.426, or 618 and 426 thousandths. And we're done.