y varies inversely with x. If y = 40 when x = 16, find x when y = -5

Question

none at this time I don't remember how to solve these types of equations

Answer 1

Since y varies inversely as x, y = k/x, for some number, k.

 

y = 40 when x = 16, so 40 = k/16. 

 

Therefore, k = 640

 

So, y = 640/x

 

When y = -5, we have -5 = 640/x

 

                                  -5x = 640

 

                                     x = -128