Suppose that z varies jointly with x and y.

Question

Find the constant of proportionality k if z = 270 when y = 9 and x = 15.

k= _____

Using the k from above write the variation equation in terms of x and y.

z= _____

Using the k from above find z given that y = 26 and x = 37.

z= _____

Answer 1

z varies directly as x and y:

z = kxy

find constant of variation (k) given x = 9, y = 15 and z = 270

270 = k*9*15

k = 2

re-write equation with computed k:

z = 2xy

find z given x = 26 and y = 37

z = 2*26*37 = 1924