Do Now Multiply. 24.5  7 2. 5.4  -6.2 171.5 3. (-19.21)  (–2.1) -33.48 40.341

Homework p106 28) -19.68 36) 30.495 30) 16.6 38) -0.7728 32) -0.0876 34) -488.85 40) $ 319.63

Learn to divide decimals.

In order to divide BY a decimal, the decimal divisor must be changed into an integer. To change a decimal divisor, move the decimal point all the way to the right, noting how many places you had to move it (what you are really doing is repeatedly multiplying by 10). Now, change the dividend by moving the decimal point the same number of times. THE DIVIDEND MAY STILL BE A DECIMAL NUMBER.

The rules regarding negative decimals is the same as with integers: Same signs positive Different signs negative

Example A Divide. 8.28 ÷ 4.6 Multiply both numbers by 10 to make the divisor an integer. 8.28 ÷ 4.6 = 82.8 ÷ 46 1. 8 46 ) 82.8 Divide as with whole numbers. – 46 36 8 –36 8 Multiply both numbers by the least power of ten that will make the divisor an integer. Helpful Hint

Example A Divide. 18.48 ÷ (–1.75) 18.48 ÷ (–1.75) = 1848 ÷ 175 Multiply both numbers by 100 to make the divisor an integer. 1 .5 6 Use zeros as placeholders 175 ) 1848 . 00 –175 Divide as with whole numbers. 9 8 –87 5 10 50 –10 50 18.48 ÷ (–1.75) = –10.56 The signs are different.

Example A Divide. –24 ÷ (–2.5) –24.0 ÷ (–2.5) = –240 ÷ (–25) Multiply both numbers by 10. 9 . 6 25 ) 240 . Divide as with whole numbers. – 225 15 – 15 0

Example B Jace took a trip in which he drove 350 miles. During the trip his truck used 12.5 gallons of gas. What was his truck’s gas mileage? 350.0 ÷ 12.5 = 3500 ÷ 125 Multiply both numbers by 10. 2 8 Divide as with whole numbers. 125 ) 3500 –250 To calculate miles per gallon, divide the number of miles driven by the number of gallons of gas used. Helpful Hint 100 –1000 Jace’s truck’s gas mileage was 28 miles per gallon.

Lesson Quiz Divide. Estimate to check whether each answer is reasonable. 1. 78.2 ÷ 0.04 2. –9.72 ÷ 2.7 3. 18.88 ÷ 1.6 4. 19.5 ÷ 3.25 5. Jordan used 32.46 gallons of gas to drive his van 584.28 miles. How many miles did Jordan get per gallon? 1,995 –3.6 11.8 6 18

6. Divide. 87.3 ÷ 0.09 A. 873 B. 970 C. 977 D. 1230

7. Divide. –14.72 ÷ (3.2) A. –4.6 B. –5 C. –5.2 D. –5.6

8. Divide. 19.98 ÷ 1.8 A. 11.4 B. 11.3 C. 11.2 D. 11.1

9. Divide. 17.15 ÷ 2.45 A. 7 B. 8 C. 9 D. 10

10. Chris drives at an average speed of 55. 45 miles per hour 10. Chris drives at an average speed of 55.45 miles per hour. How long does it take for him to travel a distance of 388.15 miles? A. 6 hours B. 7 hours C. 8 hours D. 9 hours