The simple interest at x% for x years will be Rs. x on a sum of:

Answer: Option B

$$\begin{array}{rl}& \text{Sum}=\frac{100\times S.I.}{R\times T}\\ & =\text{Rs}\text{.}\frac{100\times x}{x\times x}\\ & =\text{Rs}\text{.}\frac{100}{x}\end{array}$$