Practice and Problem-Solving Exercises

A Practice

See Problem 1.

Suppose y varies inversely with x. Write an equation for the inverse variation.

9. y = 6 y equals 6  when x = 3 x equals 3
10. y = 1 y equals 1  when x = − 2 x equals negative 2
11. y = 7 y equals 7  when x = 8 x equals 8
12. y = 3 y equals 3  when x = 0.5 x equals 0.5
13. y = − 10 y equals negative 10  when x = − 2.4 x equals negative 2.4
14. y = 3.5 y equals 3.5  when x = 2.2 x equals 2.2

    See Problem 2.

15. Travel A family takes 2 1 2 2 , and 1 half  h to drive from their house to a lake at 48 mi/h. The travel time varies inversely with the speed of the car. How long will the return trip take at 40 mi/h?
16. Bicycling A camper takes 2 h to ride a bike around a reservoir at 10 mi/h at the beginning of the summer. By the end of the summer, she can ride around the reservoir in 1 1 2 1 , and 1 half  h. The time to travel around the reservoir varies inversely with the speed she pedals. What is her speed at the end of the summer?

See Problem 3.

Graph each inverse variation.

17. y = 9 x y equals , 9 over x
18. x y = 12 x y equals 12
19. y = − 15 x y equals , negative 15 over x
20. 14 x = y 14 over x , equals y
21. 20 = x y 20 equals x y
22. y = 7.5 x y equals , 7.5 over x
23. x y = − 24 x y equals negative 24
24. y = − 1 x y equals , negative 1 over x

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