Question

The variable z is directly proportional to x, and inversely proportional to y. When x is 6 and y is 6, z has the value 12.

Answer 1

z is directly proportional to x: z = kx.

If z is directly proportional to x and inversely proportional to y, then z = Kx/y.

When x= 6 and y = 6, z is 12. Find the constant of proportionality, K:

12 = K(6/6), or K = 12

Then, in general, z = 12x/y.

What is z when x=13 and y=10? z = 12(13)/(10) = 15.6 (answer)