Adding and Subtracting Decimals

1. Adding and Subtracting Decimals

2. Essential Question: • How do I add and subtract decimals? • Always line up decimals • Add and subtract like you always do • Bring decimal straight down in your answers

3. Adding Examples: 4.55 + 11.3 Put the first number on the top of the second number and line up the decimals. You can add a zero to help keep everything lined up When adding or subtracting you always start from the right and work left. 4.55 + 11.3 0 15.85

4. 6.44 + 16 When there is not a decimal put one behind the number. Line up the decimal Add a zero to line up everything 6.44 + 16. 0 22.44

5. -8.33 + -10.972 -8.33 -10.972 Line up the decimal Add a zero to line up everything 0 + Same signs Add – keep the sign -19.302

6. Subtracting Examples: 5.34 -2.08 Put the first number on the top of the second number and line up the decimals. Different signs Take difference 5.34 -2.08 3.26

7. -38.59 – (-7.81) -38.59 + 7.81 Line up the decimal + -30.78 Subtract to add when negatives are used. Different signs take difference

8. 28 – 15.911 When there is not a decimal put one behind the number. Add zeros to line up everything, then subtract 7 9 9 28. -15.911 000 . 1 2 0 8 9

9. Magic Square The sum of each row, column, and diagonal must be the same. Sums to 13.875