Presentation Transcript
Addition & Subtraction of Decimals: Addition andamp; Subtraction of Decimals by
Doug McFarland
Horizon Academy
Roeland Park, Kansas
www.horizon-academy.com
Add and Subtract like Columns: Add and Subtract like Columns 71 + 58 + 25 = _______ 4 1 15 RULE: Only add and subtract LIKE columns.
Slide3: 7.1 + 5.8 + 2.5 = _______ Add andamp; Subtract like Columns . 4 1 15 RULE: Only add and subtract LIKE columns.
The “Understood” Decimal: 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).
Addition with the “Understood” Decimal: 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.
Make The Columns Even: Make The Columns Even 34.5 + 21 + 8.5 .0 34.5
21.0
8.5 + RULE: Add zeros to even the columns
Make The Columns Even: Make The Columns Even 44.589 + 7.23 + 5 56.819 1 1 7 23 0 5 000
Subtracting Decimals: 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.
Let’s Look at Subtraction: Let’s Look at Subtraction 34 – 12 = _____
Subtract Similar Columns: Subtract Similar Columns 34 – 1.2 = _____ RULE: Only add and subtract LIKE columns.
Subtract Similar Columns: Subtract Similar Columns 34 – 1.2 = _____
1 8 2 3
Here’s a Tricky One: Here’s a Tricky One 8 - 3.56 = _______ .00 5.56 1 1 4. 4 4
We’re Done!: We’re Done!
Nice job following along in the lesson!
Try to use what you learned in your work!
Doug McFarland ©2006