Find an equation of variation in which y varies jointly as x and z, and y = 18 when x = 2 and z = 9.
Since y varies jointly x and z, use the form y = k * x * z.
To find the variation constant, substitute 18 for y, 2 for x, and 9 for z.
18 = k*2*9
Solve for k.
18 = 18k
1 = k
There variation constant is 1.
The equation of variation is y = x*z.