The variable z is directly proportional to x, and inversely proportional to y. When x is 10 and y is 2, z has the value 45. What is the value of z when x= 15, and y= 12.

Answer 1

z = kx/y

45 = k*10/2

k = 9

so z (x,y) = 9x/y

z(15,12) = 9*15/12 = (3/4)(15) = 45/4 = 11 and 1/4 = 11.25