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ADDING AND SUBTRACTING DECIMALS PowerPoint Presentation
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ADDING AND SUBTRACTING DECIMALS

ADDING AND SUBTRACTING DECIMALS

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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.