The square root of ( 272^2 - 128^2 ) is = ?

Answer: Option C

$$\begin{array}{rl}& =\sqrt{\left({272}^2-{128}^2\right)}\\ & =\sqrt{\left(272+128\right)\left(272-128\right)}\\ & =\sqrt{400\times 144}\\ & =\sqrt{57600}\\ & =240\end{array}$$