Question

z varies jointly with x and y. When x = 2 and y = 3, z = 60. What is the value of z when x = 4 and y = 9?

Answer 1

When it says z varies jointly, it means z=kxy where k is constant.
x*y=6
60=k*6
k=10

Now plug in the new given values for x and y
z=10*4*9
z=40*9
z=360

Final answer: 360

Answer 2

2 x 3 = 6 x 10 = 60
Assuming that you are using the same rule:
4 x 9 x 10 = 360
The value of z when x = 4 and y = 9 is 360. Hope this helped!