RATES AND UNIT RATES 7.. 7.. Rate of change is a ratio that describes how one quantity is changing with respect to another. Unit rate is a rate that compares the change in one quantity to a one-unit change in another quantity. Some examples of rates are miles per hour and price per pound. If 6 ounces of flour cost $0.80 then the unit cost, that is the cost per one once, is $0.80 6 $0.05. For additional information see the Math Notes box in Lesson 7.. of the Core Connections, Course text. Example A rice recipe uses 6 cups of rice for 5 people. At the same rate, how much rice is needed for 0 people? The rate is: 6 cups 5 people so we need to solve 6 5 x 0. The multiplier needed for the Giant One is 0 5!or. Using that multiplier yields 6 Note that the equation 6 5 x 0 5! 6 0 so 6 cups of rice is needed. can also be solved using proportions. Example Arrange these rates from least to greatest: 0 miles in 5 minutes 60 miles in one hour 70 miles in hr Changing each rate to a common denominator of 60 minutes yields: 0 mi 5 min x > 0 60 5!.. 7 60 mi min 60 mi hr 60 mi 70 mi 60 min 70 mi hr 00 min x 60 > 70 00! 0.6 mi 0.6 60 min So the order from least to greatest is: 70 miles in hr < 60 miles in one hour < 0 miles in 5 minutes. Note that by using 60 minutes (one hour) for the common unit to compare speeds, we can express each rate as a unit rate: mph, 60 mph, and 7 mph. Parent Guide with Extra Practice 59
Example A train in France traveled 9 miles in 5 hours. What is the unit rate in miles per hour? 9 mi x 5 hr hr Unit rate means the denominator needs to be hour so: One of 0. or simple division yields x 86. miles per hour. 0.. Solving by using a Giant Problems Solve each rate problem below. Explain your method.. Balvina knows that 6 cups of rice will make enough Spanish rice to feed 5 people. She needs to know how many cups of rice are needed to feed 5 people.. Elaine can plant 6 flowers in 5 minutes. How long will it take her to plant 0 flowers at the same rate?. A plane travels 00 miles in 8 hours. How far would it travel in 6 hours at this rate?. Shane rode his bike for hours and traveled miles. At this rate, how long would it take him to travel miles? 5. Selina s car used 5.6 gallons of gas to go miles. At this rate, how many gallons would it take her to go 80 miles? 6. Arrange these readers from fastest to slowest: Abel read 50 pages in 5 minutes, Brian read 90 pages in 75 minutes, and Charlie read 75 pages in hours. 7. Arrange these lunch buyers from greatest to least assuming they buy lunch 5 days per week: Alice spends $ per day, Betty spends $5 every two weeks, and Cindy spends $75 per month. 8. A train in Japan can travel 8.5 miles in 5 hours. Find the unit rate in miles per hour. 9. An ice skater covered 500 meters in 06 seconds. Find his unit rate in meters per second. 0. A cellular company offers a price of $9.95 for 00 minutes. Find the unit rate in cost per minute.. A car traveled 00 miles on 8 gallons of gas. Find the unit rate of miles per gallon and the unit rate of gallons per mile.. Lee s paper clip chain is feet long. He is going to add paper clips continually for the next eight hours. At the end of eight hours the chain is 80 feet long. Find the unit rate of growth in feet per hour.. 5 cups. 75 min. 550 miles. hr 5. gallons 6. C, B, A 7. C, A, B 8. 6.7 mi/hr 9.!.5 m/s 0.! $0.0 /min. 5 m/g; g/m 5. 6 ft/hr 60 Core Connections, Course
DIVISION BY FRACTIONS 7.. 7., Division by fractions introduces three methods to help students understand how dividing by fractions works. In general, think of division for a problem like 8 as, In 8, how many groups of are there? Similarly,!! means, In, how many fourths are there? For more information, see the Math Notes box in Lessons 7.. and 7.. of the Core Connections, Course text. For additional examples and practice, see the Core Connections, Course Checkpoint 8B materials. The first two examples show how to divide fractions using a diagram. Example Use the rectangular model to divide:!!. Step : Step : Using the rectangle, we first divide it into equal pieces. Each piece represents. Shade of it. Then divide the original rectangle into four equal pieces. Each section represents. In the shaded section,, there are fourths. Step : Write the equation.!! Example In, how many s are there? In there is one full That is,? shaded and half of another one (that is half of one-half). Start with. So: (one and one-half halves) Parent Guide with Extra Practice 6
Problems Use the rectangular model to divide..!! 6.!!.!!.!! 5.!! 9. 8 rds 6ths. halves quarters. one fourths 8 sixths. quarters halves three fourths 5. rds 9ths fourths halves ninths The next two examples use common denominators to divide by a fraction. Express both fractions with a common denominator, then divide the first numerator by the second. Example Example 5!>! 5 0 5!>! 0!>! 6 5 or 5 6!>! 6 >! 8 6 6!>! 8!or 8 6 Core Connections, Course
One more way to divide fractions is to use the Giant One from previous work with fractions to create a Super Giant One. To use a Super Giant One, write the division problem in fraction form, with a fraction in both the numerator and the denominator. Use the reciprocal of the denominator for the numerator and the denominator in the Super Giant One, multiply the fractions as usual, and simplify the resulting fraction when possible. Example 5 Example 6!! 6 6 6 8 9 Example 7 Example 8! 8 9 8 9!! 5!!!0 5!!!! 9 5!!!!0 9 Compared to:! 5 5 5 0 9 0 9 9 Problems Complete the division problems below. Use any method.. 6. 7 8. 7. 7. 7 5. 6 7 5 8 0 5 7 7. 5 8 8. 7 9. 5 0.. 5 6.. 5 8. 0 6 5. 5 6. 7. 6 7. 5 7. 5 7 6. 50 5. 5 7. 5 8. 9. 0. 5 9.... 6 5. 0 Parent Guide with Extra Practice 6
OPERATIONS WITH DECIMALS 7.. ARITHMETIC OPERATIONS WITH DECIMALS ADDING AND SUBTRACTING DECIMALS: Write the problem in column form with the decimal points in a vertical column. Write in zeros so that all decimal parts of the number have the same number of digits. Add or subtract as with whole numbers. Place the decimal point in the answer aligned with those above. MULTIPLYING DECIMALS: Multiply as with whole numbers. In the product, the number of decimal places is equal to the total number of decimal places in the factors (numbers you multiplied). Sometimes zeros need to be added to place the decimal point. DIVIDING DECIMALS: When dividing a decimal by a whole number, place the decimal point in the answer space directly above the decimal point in the number being divided. Divide as with whole numbers. Sometimes it is necessary to add zeros to the number being divided to complete the division. When dividing decimals or whole numbers by a decimal, the divisor must be multiplied by a power of ten to make it a whole number. The dividend must be multiplied by the same power of ten. Then divide following the same rules for division by a whole number. For additional information, see the Math Notes box in Lesson 5.. of the Core Connections, Course text. For additional examples and practice, see the Core Connections, Course Checkpoint, Checkpoint 7A, and Checkpoint 8B materials. Example Add 7.7, 8.9,.56, and 7.8. 7.7 8.90.56 + 7.80 98.6 Example Multiply 0.7 by 0.000. 0.7 ( decimal places ) x 0.000 ( decimal places) 0.0008 (6 decimal places) Example Subtract 98.76 from 7.. 7.0! 98.76 7. Example 5 Divide. by 8..05 8).0 0 0 0 0 Example Multiply 7. by.5. 7. ( decimal places ) x. 5 ( decimal places ) 896 660 098 7 96.9596 ( decimal places) Example 6 Divide 7. by.. First multiply each number by 0 or 0..85. 7.! 7.! 7.0 0 96 60 60 0 6 Core Connections, Course
Problems..7 + 7.9..9 +.8. 8.7 + 6.7. 58. + 7.8 5..7 + 69 6. 8 + 7.9 7..08 +.7 8. 9.87 + 87.796 9. 9.999 + 0.00 0. 0.000 + 99.9999. 0.07 +.78..07 + 0.0987. 5. + 7.89. 7.9 + 68.07 5. 89.07 + 5.98 6. 76.8 + 7.87 7. 5.8 + 7. + 9.076 8. 8. + 8. +.68 9. 78.6 + 7.0 +.6 0. 7.68 + 8.0076 + 8.. 8.7.6. 9.8 7.5. 8. 6.98. 7.05.76 5. 6.0.68 6. 8.0.7 7. 7. 8. 5.7 9. 0.65 0. 8 9.0. 0.8 0.7. 0.67 0.9.. 0.058..07 0.5 5...76 6..8.06 7. 8..605 8. 7..70 9. 5.68 +. 8.576 0. 87. 5.687 8.06. 7. 6...7.0. 0.08.7. 0.0.75 5..6 0.0 6. 9. 0.005 7..07 5. 8..0.0 9. 0.00 0.005 50. 0.007 0.000 5. 0.5 0. 5.. 0.007 5. 0.0006 0.000 5. 0.0005 0.0006 55. 8.8 0.000 56. 7.6 0.00000 57. 0.078. 58. 0.0. 59. 50 0.00 60. 0.00005 Parent Guide with Extra Practice 65
Divide. Round answers to the hundredth, if necessary. 6.. 8 6. 8. 5 6. 7. 6 6. 6.6 65. 00. 66..7 8 67. 7. 0.00 68. 5.6 0.00 69. 500 0.00 70. 0 0.05 7.. 0.0 7..86 0.0 7. 6. 0.0 7. 5.7 0.0 75. 5.6 5.05 76. 6.5. 77. 6.0 0.006 78. 7.05 0.005 79. 07.. 80. 06....6. 6.75. 5... 5. 696.7 6. 5.9 7. 56.88 8. 97.96 9. 0.000 0. 00.0000..797..087. 88.9. 5.97 5. 05.5 6. 50. 7. 5.856 8. 7.58 9. 7.7 0. 59.9876....88....85 5..6 6..65 7. 6.569 8. 7.6 9. 5.8 0. 8.957. 0.6. 0.57..86..57 5..6 6..9 7. 5.85 8..7 9..0 0..7067. 6.976..95. 0.76. 0.5 5..56 6. 0.098 7. 6.578 8..96 9. 0.00000 50. 0.000008 5. 0.005 5. 0.00 5. 0.000000078 5. 0.0000000 55. 0.00088 56. 0.00076 57. 0.8 58. 0.806 59.. 60. 0.005 6..7875 or.79 6..66 or.66 6..55 6..86 or.86 65..8 66..7 67.,650 68.,00 69. 5,000 70. 800 7..5 7. 9.05 7. 09.09 7..78 75. 5.0 76..98 77. 007 78. 07 79. 7. 80. 95.75 66 Core Connections, Course
GRAPHING AND SOLVING INEQUALITIES 7.. GRAPHING INEQUALITIES The solutions to an equation can be represented as a point (or points) on the number line. If the expression comparison mat has a range of solutions, the solution is expressed as an inequality represented by a ray or segment with solid or open endpoints. Solid endpoints indicate that the endpoint is included in the solution ( or ), while the open dot indicates that it is not part of the solution (< or >). For additional information, see the Math Notes box in Lesson 7.. of the Core Connections, Course text. Example x > 6 Example y < 6 0 6 Example x 0 Example y 0 6 0 Problems Graph each inequality on a number line.. m <. x. y. x 5. 6 < x < 6. < x 7. m > 9 8. x 9. x.... 5. 6. 6 7. 8. 9. 9 Parent Guide with Extra Practice 67
SOLVING INEQUALITIES To solve an inequality, examine both of the expressions on an expression comparison mat. Use the result as a dividing point on the number line. Then test a value from each side of the dividing point on the number line in the inequality. If the test number is true, then that part of the number line is part of the solution. In addition, if the inequality is or, then the dividing point is part of the solution and is indicated by a solid dot. If the inequality is > or <, then the dividing point is not part of the solution, indicated by an open dot. Example 9 m + Solve the equation: 9 m + 7 m Draw a number line. Put a solid dot at 7. Test a number on each side of 7 in the original inequality. We use 0 and 0. TRUE 7 FALSE Example x < x + 6 Solve the equation: x x + 6 x x + 9 x 9 x Draw a number line. Put an open dot at. Test 0 and in the original inequality. FALSE TRUE m 0 9 > 0 + 9 > TRUE 7 m 0 9 > 0 + 9 > FALSE x ( ) < + 6 8 < 5 < x 0 (0) < 0 + 6 < 6 TRUE The solution is m 7. FALSE The solution is x >. 7 68 Core Connections, Course
Problems Solve each inequality.. x + >. y 5. x 6. m + 7 5. 7 < y + 6. 8 m + 7. x < x + 8 8. (m + ) m 9. m + m + 7. x >. y 8. x. m 5. y < 5 6. m 7. x < 8. m 5 9. m Parent Guide with Extra Practice 69