$z$ varies directly as the square of $x$ and inversely as $y$. If $z = 8$ when $x = 2$ and $y = 2$, find $z$ when $x = 4$ and $y = 8$.

If a dust storm reduces the UV intensity to , how many liters of oxygen will of algae walls produce? 2. The Gravity Train (Combined Variation) The time (

: Occurs when one quantity varies directly as the product of two or more other quantities. Formula : is the constant).