Practice and Problem-Solving Exercises

A Practice

See Problem 1.

Is the relationship between the values in each table a direct variation, an inverse variation, or neither? Write equations to model the direct and inverse variations.

6. x	y
   3	15
   8	40
   10	50
   22	110

7. x	y
   3	15
   5	8.4
   7	6
   10.5	4

8. x	y
   0.5	1
   2.1	8.4
   3.5	7
   11	22

9. x	y
   0.1	3
   3	0.1
   6	0.05
   24	0.0125

See Problem 2.

Suppose that x and y vary inversely. Write a function that models each inverse variation. Graph the function and find y when x = 10.

10. x = 1 x equals 1  when y = 11 y equals 11
11. x = − 13 x equals negative 13  when y = 100 y equals 100
12. x = 1 x equals 1  when y = 1 y equals 1
13. x = 1 x equals 1  when y = 5 y equals 5
14. x = 1.2 x equals 1.2  when y = 3 y equals 3
15. x = 2.5 x equals 2.5  when y = 100 y equals 100
16. x = 20 x equals 20  when y = − 4 y equals negative 4
17. x = 5 x equals 5  when y = − 1 3 y equals negative , 1 third
18. x = − 4 15  when  y = − 105 x equals negative , 4 fifteenths . when , y equals negative 105

See Problem 3.

19. Fundraising In a bake sale, you recorded the number of muffins sold and the amount of sales in a table as shown.

    Number of muffins (m)	Sales (s)
    5	$12.50
    8	$20.00
    13	$32.50
    20	$50.00

    1. What is a function that relates the sales and the number of muffins?
    2. How many muffins would you have to sell to make at least $250.00 in sales?

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