When e = 4, f = 2, and g = 8. If e varies jointly with f and g, what is the constant of variation?

In joint variation, the equation of variation holds the form

e=k*fg, where k is the constant of variation. you can see how if either f or g increases, e increases as well, making e vary jointly with f and g. we are given the numbers e=4, f=2, and g=8, so when we input those into the general equations,

4=k*2*8,

k=1/4