Question

I BET NO ONE KNOWS THIS y varies jointly as x and z. y=20 when x=2 and z=5 . Find y when x=3 and z=6

Answer 1

Hello!

If y varies jointly with x and z, it'll mean that x and z are being multiplied by a factor "k", to equal y.

To give you a visual, this is what I mean.

$y=kxz$

That means we'll want to find $k$ with the first point we're given: $(2,20,5)$

$20=k(2)(5)$

$20=10k$

$k=2$

Which means our equation is:

$y=2xz$

Now, let's plug in the $x$ and $z$ from the other point to find $y$.

$y=2(3)(6)$

$y=36$

Hope this helps!