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?
A. 360
B. 60
C. 90
D. 40

Answer 1

Varying jointly would mean

\[\large z = kxy\]

Answer 2

So when z = 60, x = 2 and y = 3 we have

\[\large 60 = k(2)(3)\]

Solve for 'k'

Answer 3

so k=10

Answer 4

Right...and you've seen this before correct?

varying jointly..and 'k' being the constant of variation...

Answer 5

so A?

Answer 6

A would be correct :)

Answer 7

yay thank you!

Answer 8

Anytime :)