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ADDING AND SUBTRACTING DECIMALS

ADDING AND SUBTRACTING DECIMALS. SECTION 1.07. 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. ones. ten ths. 7 . 1

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ADDING AND SUBTRACTING DECIMALS

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  1. ADDING AND SUBTRACTING DECIMALS SECTION 1.07

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

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

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

  6. 33 ones tenths 34. 0 - 1. 2 . Subtract Similar Columns 34 – 1.2 = _____ 3 2 8

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

  8. 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, $ 7.89 Can you buy all 3 games using the gift certificate? • Add the front-end digits $8 + 7 + 7 = $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.

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