Please help with this word problem. I'm not understanding this concept and I have to show all of the work.

Question

Suppose x and y vary inversely, and y = 10 when x = 4. Write a function that models the variation (1pt.). Then find y when x = 90 (1pt.).

 

Thank you

Answer 1

Inverse relation:

 

xy = k,

 

where k is a constant.

 

x = 4 and y = 10 ⇒ k = xy = 4(10) = 40

 

xy = 40

 

y = 40/x

 

x = 90 ⇒ y = 40/90 = 4/9