The simple interest at x % for x years will be Rs x for a principal amount of

(c) P = 100\over x

Explanation

Simple Interest (I) = \frac{\text{P × r × t}}{100}

or, x = \frac{\text{P × x × x}}{100}

or, P = \frac{\text{ x × 100}}{x × x}

or, P = 100\over x