A sum of money doubles itself in 10 years at simple interest. What is the rate of interest per annum?

यदि मूलधन = P, मिश्रधन = 2P, तो ब्याज = P। I = (P x R x T) / 100 का उपयोग करते हुए: P = (P x R x 10) / 100, R = 100 / 10 = 10%.