If x% of y is equal to z, what percent of z is x ?

Answer: Option D

x% of y = z
⇒ $$\frac{x}{100}$$y = z
⇒ $$\frac{x}{z}$$ = $$\frac{100}{y}$$
∴ Required percentage
$$\begin{array}{rl}& =\left(\frac{x}{z}\times 100\right)\%\\ & =\left(\frac{100}{y}\times 100\right)\%\\ & =\left(\frac{{100}^2}{y}\right)\%\end{array}$$