Addition & Subtraction of Decimals by Doug McFarland Horizon Academy Roeland Park, Kansas www.horizon-academy.com

by

Doug McFarland

Horizon Academy

Roeland Park, Kansas

www.horizon-academy.com

Add and Subtract like Columns 71 + 58 + 25 = _______ 4 1 15 RULE: Only add and subtract LIKE columns. 71 58 25 + tens ones

7.1 + 5.8 + 2.5 = _______ Add & Subtract like Columns . 4 1 15 RULE: Only add and subtract LIKE columns. 7 . 1 5 . 8 2 . 5 + ones ten ths

The “Understood” Decimal Consider the whole number 15 15 = 1 ten + 5 ones (10 + 5). We could put a decimal to separate the whole number from the decimal. 15.0 There is NO value in the tenths column, so we put 0 (zero).

Consider the whole number 15

15 = 1 ten + 5 ones (10 + 5).

We could put a decimal to separate the whole number from the decimal.

15.0 There is NO value in the tenths column, so we put 0 (zero).

Addition with the “Understood” Decimal If you were adding 15 + 12 you could write the problem 15.0 + 12.0 15.0 + 12.0 = 27.0 or 27 When there is no decimal value, the zero and the decimal are NOT written, but they are understood to still be there.

If you were adding 15 + 12 you could write the problem 15.0 + 12.0

15.0 + 12.0 = 27.0 or 27

When there is no decimal value, the zero and the decimal are NOT written, but they are understood to still be there.

Make The Columns Even 34.5 + 21 + 8.5 .0 34.5 21. 0 8.5 + RULE: Add zeros to even the columns 34.5 21 8.5 +

34.5 + 21 + 8.5

Make The Columns Even 44.589 + 7.23 + 5 56.819 1 1 7 23 0 5 000 3 decimal columns 2 decimal columns 0 decimal columns 44.589 . . +

44.589 + 7.23 + 5

Subtracting Decimals Remember how to even your columns. Remember the “understood” . 0 when looking at a whole number like 7 It could be 7. 0 or 7. 00 if needed . In subtraction, it will be needed .

Remember how to even your columns.

Remember the “understood” . 0 when looking at a whole number like 7

It could be 7. 0 or 7. 00 if needed .

In subtraction, it will be needed .

Let’s Look at Subtraction 34 – 12 = _____ 34 - 12 22 tens ones

34 – 12 = _____

Subtract Similar Columns 34 – 1 . 2 = _____ RULE: Only add and subtract LIKE columns. 3 4 - 1.2 2.2 ones ones ten ths tens Warning ! !

34 – 1 . 2 = _____

Subtract Similar Columns 34 – 1.2 = _____ 1 8 2 3 34. 0 - 1. 2 . ones ten ths 3 33

34 – 1.2 = _____

Here’s a Tricky One 8 - 3.56 = _______ .00 5.56 1 1 4. 4 4 8 - 3.56 8. 0 0 - 3. 5 6 7 9

8 - 3.56 = _______

We’re Done! Nice job following along in the lesson! Try to use what you learned in your work! Doug McFarland ©2006

Nice job following along in the lesson!

Try to use what you learned in your work!

Doug McFarland ©2006