# Course 3 2-1 Rational Numbers 2-1 Rational Numbers Course 3 Warm Up Warm Up Problem of the Day Problem of the Day Lesson Presentation Lesson Presentation.

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Course 3 2-1 Rational Numbers 2-1 Rational Numbers Course 3 Warm Up Warm Up Problem of the Day Problem of the Day Lesson Presentation Lesson Presentation

Course 3 2-1 Rational Numbers Warm Up Divide. 12 24 3 4 16 1. 36  3 2. 144  6 3. 68  17 4. 345  115 5. 1024  64

Course 3 2-1 Rational Numbers Problem of the Day An ice cream parlor has 6 flavors of ice cream. A dish with two scoops can have any two flavors, including the same flavor twice. How many different double-scoop combinations are possible? 21

Course 3 2-1 Rational Numbers Learn to write rational numbers in equivalent forms.

Course 3 2-1 Rational Numbers rational number relatively prime Vocabulary

Course 3 2-1 Rational Numbers A rational number is any number that can be written as a fraction, where n and d are integers and d  0. n d

Course 3 2-1 Rational Numbers The goal of simplifying fractions is to make the numerator and the denominator relatively prime. Relatively prime numbers have no common factors other than 1.

Course 3 2-1 Rational Numbers You can often simplify fractions by dividing both the numerator and denominator by the same nonzero integer. You can simplify the fraction to by dividing both the numerator and denominator by 3. 12 of the 15 boxes are shaded. 4 of the 5 boxes are shaded. The same total area is shaded. 12 15 4 5 = 12 15 4 5

Course 3 2-1 Rational Numbers Additional Example 1A: Simplifying Fractions 16 80 16 = 1 16 80 = 5 16 ;16 is a common factor. 1515 = 16 80 Divide the numerator and denominator by 16. = 16 ÷ 16 80 ÷ 16 Simplify. = 0 for a ≠ 0 = 1 for a ≠ 0 = = – Remember! 0a0a a –7 8 7 –8 7878

Course 3 2-1 Rational Numbers = –18 29 –18 29 18 = 2 9 29 = 1 29 ;There are no common factors. –18 and 29 are relatively prime. –18 29 Simplify. Additional Example 1B: Simplifying Fractions

Course 3 2-1 Rational Numbers 18 27 ; 9 is a common factor. 2323 = 18 27 = 18 ÷ 9 27 ÷ 9 Divide the numerator and denominator by 9. Check It Out: Example 1A Simplify. 18 = 3 3 2 27 = 3 3 3

Course 3 2-1 Rational Numbers = – 17 35 17 –35 17 = 1 17 35 = 5 7 ; There are no common factors. 17 and –35 are relatively prime. 17 –35 Check It Out: Example 1B Simplify.

Course 3 2-1 Rational Numbers Decimals that terminate or repeat are rational numbers. To write a terminating decimal as a fraction, identify the place value of the digit farthest to the right. Then write all of the digits after the decimal point as the numerator with the place value as the denominator.

Course 3 2-1 Rational Numbers Rational Number Description Written as a Fraction –3.2 Terminating decimal 0.16 Repeating decimal –32 ___ 10 1 __ 6

Course 3 2-1 Rational Numbers 5.37 A. 5.37 7 is in the hundredths place. 37 100 = 5= 5 Additional Example 2: Writing Decimals as Fractions Write each decimal as a fraction in simplest form. 0.622 B. 0.622 2 is in the thousandths place. 622 1000 = = 311 500 Simplify by dividing by the common factor 2.

Course 3 2-1 Rational Numbers 8.75 A. 8.75 5 is in the hundredths place. 75 100 = 8= 8 = 8= 8 3434 Simplify by dividing by the common factor 25. Write each decimal as a fraction in simplest form. Check It Out: Example 2 0.2625 B. 0.2625 5 is in the ten-thousandths place. 2625 10,000 = = 21 80 Simplify by dividing by the common factor 125.

Course 3 2-1 Rational Numbers denominator numerator To write a fraction as a decimal, divide the numerator by the denominator. You can use long division. numerator denominator

Course 3 2-1 Rational Numbers 9 11 The pattern repeats. 1 –9.2 2 0.0 2 11 9 –1 8 Additional Example 3A: Writing Fractions as Decimals Write the fraction as a decimal. The fraction is equivalent to the decimal 1.2. 11 9 A repeating decimal can be written with a bar over the digits that repeat. So 1.2222… = 1.2. Writing Math _

Course 3 2-1 Rational Numbers This is a terminating decimal. 20 7.3 05 The remainder is 0. 7 20 –0 7 1 0 0 0 0.0 0 –6 0 –1 0 0 Additional Example 3B: Writing Fractions as Decimals Write the fraction as a decimal. The fraction is equivalent to the decimal 0.35. 7 20

Course 3 2-1 Rational Numbers 9 15 The pattern repeats, so draw a bar over the 6 to indicate that this is a repeating decimal. 1 –9.6 6 0.0 6 15 9 –5 4 Write the fraction as a decimal. Check It Out: Example 3A The fraction is equivalent to the decimal 1.6. 15 9

Course 3 2-1 Rational Numbers 40 9 This is a terminating decimal..2 02 The remainder is 0. 9 40 –0 9 1 0 0 0.0 0 –8 0 – 8 0 2 0 0 0 5 0 – 2 0 0 Write the fraction as a decimal. Check It Out: Example 3B The fraction is equivalent to the decimal 0.225. 9 40

Course 3 2-1 Rational Numbers Lesson Quiz: Part 1 Simplify. 1.2. Write each decimal as a fraction in simplest form. 3. 0.27 4. –0.625 5. Write as a decimal 2.16 18 42 3737 15 21 5757 27 100 – 5858 13 6

Course 3 2-1 Rational Numbers Tommy had 13 hits in 40 at bats for his baseball team. What is his batting average? (Batting average is the number of hits divided by the number of at bats, expressed as a decimal.) Lesson Quiz: Part 2 6.6. 0.325

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