The variable z is directly proportional to x, and inversely proportional to y

Question

The variable z is directly proportional to x, and inversely proportional to y. When x is 16 and y is 5, z has the value 16.

What is the value of z when x= 21, and y= 14

Round to at least the thousandths place if needed.

Answer 1

z = kx/y

 

Since z = 16 when x = 16 and y = 5, 16 = 16k/5.  So, k = 5.

 

z = 5x/y

 

When x=21 and y = 14, z = 5(21)/14 = 7.5