Name _

..-Practice B ~ For use with pages 764 -772

.. .Tell whether the equation represents direct VariatIOn, mve or neither.

1. y= -llx 2. xy =-5

-8 4. •x=-y 5. xy = 14

7. 2x+y=8 8. 3y =:;9

11) Graph the inverse variation y,

equation: xy =-6

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Gl en-.­ .. Gl, > N.E II. . -Tell whether the table represents inverse variation. If so, write the Inverse

variation equation.

31. x 2 4 6 8 10

y II 21 31 41 51

32. x -5 -4 I 2 10

y -4 -5 20 10 2

33. x 10 23 25 28 50 y 160 368 400 448 800

34.

35. Catalog Orders A clothing company allows customers to place orders on the Internet or by phone. The orders must be entered into the computer inventory system. The number of orders n entered per person into the system varies inversely with the number p ofpeople working. The company estimates that 10 people working during a shift can get 960 orders entered.

a. Write an inverse variation equation that relates nand p.

b. Find the number of orders entered per person during a shift if 20 peopleare working.

c. Find the number of orders entered per person during a shift if 8 people are working.

36. Volume and Pressure The volume V of a gas at a constant temperature varies inversely with the pressure P. When the volwne is 125 cubic inches, the pressure is 20 pounds per cubic inch.

a. Write the inverse vaIiation equation that relates P and V.

b. Find tbe pressure of a gas with a volume of 250 cubic inches.

x -10 -9 -6 -5 -4 y -1.8 -2 -3 -3.6 -4.5

Date

rse variation,

3. Y =x - 4

~ = 136. x

9. 4x - 4y = 0

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---------- ---------LESSON 3.8 Practice B Name Date

Solve the formula for the indicated variable. 5 1. Fahrenheit to Celsius Solve for F: C = - (F - 32)

9

2. Perimeter ofa Parallelogram Solve for b: P = 2b + 2s

3. Perimeter ofa Triangle Solve for c: P = a + b + c

4. Area ofa Rhombus

5. Area ofa Trapezoid

2h6. Volume ofa Right Circular Cylinder Solve for h: V = nr

7. Lateral Surface Area ofa Right Circular Cylinder Solve for h: S = 2nrh

n 2rh8. Volume ofa Right Circular Cone Solve for h : V = -­

3

Solve the formula for the indicated variable. Then use the given information to find the value of the variable. Include units of measure in the answer.

9. Area ofa Parallelogram

Solve for h: A = bh

Find h when,A = 81 cm2 and b = 9 em.

10. Celsius to Fahrenheit

9Solve for C: F=- C + 32

5

Find C when F = 77°F.

Basketball A regulation size basketball has a volume of 455.9 cubic inches. Use this information to answer the following questions. Approximate your answers to the nearest tenth.

4

11. The formula for the volume ofa sphere is V= 3 nr3. What is the radius of the basketball?

12. What is the diameter of the basketball?

13. The formula for the circumference of the basketball is C = 2nr. If the circumference of a basketball is 29 inches, is it a regulation size basketball?

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Answer Key

Lesson 12.1

Practice Level B

1. direct v31iation 2. inverse variation 3. neither 4. inverse variation 5. inverse variation \

6. direct variation 7. neither 8. inverse variation 9. direct variation

11. ' 1 i ' ~ I \

~~,IJ,-,: -!,Ir -; II J I

14 27 27 -3 3 -II II 144 72 19.y = -;-; 7 20.y = -;-; 2 21.y = 7; -2 22.y = -x-; -2 23.y = 7; 72 24.y = -;-; 36

-28, 3.6 ' ,- -i£ -2~-~0itJ41t""'08~ ,118 S8:..y~,..._.J.~"'!Y.iZ1 p;; 1Ii" I x x Xx

20 18 9600~55 31.no 32. yes; y = - 33. no 34. yes; y = - 35. a. n =-- b. 480 orders 3'tat'1 -:;z2 x x p

V - 2500 10 lb/' 3 c. l200 orders 36. a. - p b. lll. ~