The simple interest on a sum of money is \(\frac{18}{25}\) of the sum. If the number of years is numerically half the rate per annum, then find the rate percent per annum.

12%

SI = \(\frac{18 → SI}{25→ principal}\)

Let rate = 2x%, then year = x

SI = \(\frac{P × R × T}{100}\)

18 = \(\frac{25 × 2x × x}{100}\) ⇒ x² = 36

                                                       x = 6 then rate = 2x = 12%