Answer
The diameter of the oil slick is 3000 meters.
Work Step by Step
Let $y$ be the thickness of the oil slick, which is equal to the diameter of an oil molecule. Assume that the oil slick forms a circle. Then the area $A$ of the oil slick is $\pi r^2$, where $r$ is the radius of the oil slick.
$A\cdot y = volume$
$\pi r^2 \cdot y = V$
$r = \sqrt{\frac{V}{\pi \cdot y}}$
$r = \sqrt{\frac{(1000 ~cm^3)(10^{-6} ~m^3/cm^3)}{\pi \cdot(2\times 10^{-10} ~m)}}$
$r = 1260 ~m$
The diameter is $2r$, so the diameter of the oil slick is 2520 meters. Rounding off 2520 to one significant figure, the diameter is 3000 meters.
