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Do Now 12/2/13 Copy HW in your planner. Text p. 116, #1-19 odds Benchmark Test Chapters 1,2,3, & 11 Wednesday and Thursday. Objective SWBAT review adding, subtracting, multiplying, and dividing decimals ADDITION & SUBTRACTION REVIEW Section 2.2 “Adding Integers” Adding Two Integers with SAME signs To add two integers with the SAME signs, add the absolute values of the numbers. The answer will have the same sign. 35 + 18 |35| = 35 |18| = 18 35 + 18 = 53 -35 + (-18) |-35| = 35 |-18| = 18 35 + 18 = -53 Section 2.2 “Adding Integers” Adding Two Integers with DIFFERENT signs To add two integers with DIFFERENT signs, subtract the smaller absolute value from the greater absolute value and write the sign of the integer with the greater absolute value. -35 + 18 |-35| = 35 |18| = 18 Because 35 has a greater 35 – 18 = - 17 absolute value than 18 the answer is “negative”. Section 2.3 “Subtracting Integers” When subtracting two integers, ADD the OPPOSITE of the second number to the first. 8–5= Instead of subtracting ADD the OPPOSITE!! Do the “OPP-OPP” 8“Opposite-Opposite” + (-5) = 3 ADD the OPPOSITE Section 3-1 Adding & Subtracting Decimals Add & subtract decimal numbers by lining up the decimal point. 1.2 + 0.87 1.20 +0.87 2.07 Use a zero as a placeholder so that both numbers are in the same place value 32.7 + (-62.82) |32.7| = 32.7 |-62.82| = 62.82 62.82 – 32.7 Because 62.82 has a greater absolute value than 32.7 the answer is “negative”. 62.82 – 32.70 - 30.12 Use a zero as a placeholder so that both numbers are in the same place value. -5.23 – 9.1 Add the Opposite !!! -5.23 + (-9.1) To add two integers with the SAME signs, find the sum of their absolute values. Use the sign of the two integers 5.23 + 9.10 -14.33 Use a zero as a placeholder so that both numbers are in the same place value. “Real-Life” During one month in the United States, 492.23 million commuter trips were taken on buses, and 26.331 million commuter trips were taken on light rail. How many more trips were taken on buses than on light rail? 492.230 – 26.331 465.899 million more trips were taken on buses than on MULTIPLICATION REVIEW “Multiplying Integers” Rule #1 The product of two integers with the same sign is always POSITIVE! 8 x 3 = 24 -8 · (-7) = 56 Rule #2 The product of two integers with different signs is always NEGATIVE! -6 x 3 = -18 8(-4) = -32 Section 3-2 Multiplying Decimals To multiply decimals, multiply as you would integers. To place the decimal point in the product count the number of decimal places in each factor. The product will have the same number of decimal places as the sum of the decimal places in the factors. Find the product. -2.78 x 0.8 -2.224 -2224 -2.78 · 0.8 2 decimal places 1 decimal place How many decimal places are in each number? How many decimal places are in the sum of both numbers? 3 decimal places will then be in the product! Find the product. 0.014 x -16 0084 +0140 -0.224 -0224 -16 x 0.014 3 decimal places 0 decimal places How many decimal places are in each number? How many decimal places are in the sum of both numbers? 3 decimal places will then be in the product! “Real-Life” The average snowfall in Howell, NJ is 18.55 inches per winter. What is the total amount of snowfall in inches expected over the next 2.5 years? 18.55 x 2.5 9275 37100 46.375 Inches of snowfall expected in the next 2.5 years DIVISION REVIEW Section 3-3 “Dividing Decimals” How do you divide two decimal numbers 0.6 ÷ 0.3 or 0.3 0.6 divisor By multiplying both numbers by the same power of ten, you can make the divisor an integer. Dividing by an integer is much easier than dividing by a decimal. 0.3 0.6 Multiply both numbers by 10 2 3 6 Find the quotient of -0.875 ÷ (-0.25) 0.25 0.875 Multiply both numbers by 100 to make the divisor an integer 35 25 87.5 75 12 125 Finished 25 87.5 Move the decimal point straight up, then divide as you normally would. The quotient of two integers with the same sign is always POSITIVE! “Real-Life” If Sandy and her family used 14.95 gallons of gas to drive 358.8 miles, how many miles per gallon did the car get? 14.95 358.8 24 1495 35880 The car got 24 miles per gallon 24 Homework Text p. 116, #1-19 odd Joey is in the process of buying a new vehicle. He has narrowed his options down to 2 choices. Which vehicle gets better gas mileage (mpg) and by how much? 2.5 gallons of gas can go 48.5 miles 19.4 2.5 48.5 miles per gallon 24.25 – 19.4 0 4.85 6.8 gallons of gas can go 164.9 miles 24.25 6.8 164.9 miles per gallon The car gets 4.85 more miles per gallon of gasoline than the SUV.