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Adding and Subtracting Decimals 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 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 4.55 keep + 11.30 everything lined up 15.85 When adding or subtracting you always start from the right and work left. 6.44 + 16 When there is not a decimal put one behind the number. Line up the decimal 6.44 + 16.0 22.44 Add a zero to line up everythin g -8.33 + -10.972 Line up the decimal -8.330 + -10.972 -19.302 Add a zero to line up everythin g Same signs Add – keep the sign Subtracting Examples: 5.34 -2.08 Put the first number on the top of the second number and line up the decimals. 5.34 -2.08 3.26 Different signs Take difference -38.59 – (-7.81) + Line up the decimal -38.59 + 7.81 -30.78 Subtract to add when negatives are used. Different signs take difference 28 – 15.911 When there is not a decimal put one behind the number. 7 99 28. 000 -15.911 1 2.0 8 9 Add zeros to line up everything, then subtract Magic Square 0.5 7 4.625 8.75 The sum of each row, column, and diagonal must be the same. 6.375 0.5 7 5.25 4.625 4 2.25 8.75 2.875 Sums to 13.875