A right circular cylinder has height $h$. If its **radius is doubled** (and the height kept the same), by what factor does the volume change?

$V = \pi r^{2} h$. Doubling $r$ multiplies $r^{2}$ by $4$ (since $(2r)^{2} = 4 r^{2}$). Height unchanged. So the volume is multiplied by $4$. - Trap A would be true if volume were linear in $r$. - Trap D would be true if **both** $r$ and $h$ doubled.