1. ADDING AND SUBTRACTING DECIMALS
SECTION 1.07

2. BRING YOUR DECIMAL STRAIGHT DOWN ADD OR SUBTRACT AS USUAL
RULES
LINE UP DECIMALS
If you can not drop a straight line down through your decimals, they are not lined up correctly
Add zeros as placeholders if needed
BRING YOUR DECIMAL STRAIGHT DOWN
ADD OR SUBTRACT AS USUAL

3. Add & Subtract like Columns
= _______
ones 1
tenths
7 . 1
5 . 8
2 . 5 +
RULE: Only add and subtract LIKE columns. 15
. 4

4. Make The Columns Even 34.5 + 21 + 8.5 34.5 21 8.5 + 34.5 21.0 8.5 .0 +
RULE: Add zeros to even the columns
34.5 21
8.5 +
34.5
21.0
8.5 .0 +

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

6. Subtract Similar Columns
34 – 1.2 = _____ 33
ones
tenths
34. 0 . 3 2 8

8. FRONT-END ESTIMATION
Adding the numbers in front of the decimals
Rounding the decimal numbers to the nearest whole number
Add the two sums

9. EXAMPLE
For your birthday you receive a $25 gift certificate. You want to buy 2 used video games, whose prices are: $8.79, $7.29, $ Can you buy all 3 games using the gift certificate?
Add the front-end digits
$ = $22
Estimate the sum of the remaining digits (what is behind the decimal)
.79 and .29 are about $1
.89 is about $1
$1 + $1 = $2
Add the results.
$22 + $2 = $24
The estimated sum is less then $25, so you can buy all 3 with your gift card.