Variation problem

Question

if z varies jointly as x and y, and z = 6 when x=3 and y=4, find z when x=5 and y=6

Answer 1

z = kxy      definition of joint variation

6 = k(3)(4)

6 = 12k

0.5 = k

 

z = (0.5)(5)(6)

Can you calculate?