y varies jointly as the square x and the inverse of z. When y = 24 and x = 4, z = 6. Find the constant of variation and determine the value for x when y = 15 and z = 15.

A.=135
B.=6.25
C.=√19
D.=5

Question

y varies jointly as the square x and the inverse of z. When y = 24 and x = 4, z = 6. Find the constant of variation and determine the value for x when y = 15 and z = 15.

A.=135
B.=6.25
C.=√19
D.=5

amistre64 · Answer

so

y = kx

and 

y = k/z

together:  y = kx/z,  k = yz/x  is constant

amistre64 · Answer

might be good to define k in terms of x'y'z' as opposed to the other xyz part

k = y'z'/x'  is the initial stuff

x = yz/k

x = x' (yz)/(y'z') might be a better run