ADDING AND SUBTRACTING DECIMALS SECTION 1.07

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

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

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

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

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.