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Adding and Subtracting Decimals

When adding and subtracting decimals, first, line up the decimals. We have 4.23 plus 9.075. Same with subtraction. 5.629 minus 0.45.

Then, if you have any empty spaces, you can fill in with zeroes. Adding zeroes to the back of your number, to the back of a decimal doesn’t change the value of your number. So, these numbers are still what they were. They’re still equal.

Mini-test:¬†Adding and Subtracting Decimals 

Which of the following is equal to 1/100?
A.
B.
C.
D.
E.
Which of the following is equal to 2/100?
A.
B.
C.
D.
E.
Which of the following is equal to 3/10?
A.
B.
C.
D.
E.
Which of the following is equal to 4/10000?
A.
B.
C.
D.
E.
Which of the following is smaller than 1/2?
A.
B.
C.
D.
E.

 

The next lesson: Multiplying Decimals

The following transcript is provided for your convenience.

And then, we just add or subtract like we usually would. 0 plus 5 is 5. 3 plus 7 is 10, so write your 0, carry your 1. 1 plus 2 is 3, plus 0 is 3. Bring that decimal down. 4 plus 9 is 13. So, our answer, or our sum, is 13.305.

Now, for subtraction. We’re going to do the same thing, except now, we’re subtracting. 9 minus 0 is 9. 2 minus 5, we can’t take 5 from 2, so we need to borrow from our 6, just like we usually would, and add a 1 on to our 2, which makes 12, 12 minus 5 is 7. And then, 5 minus 4 is 1. We bring our decimal down. And 5 minus 0 is 5. So, our result, or our difference, is 5.179.

 

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