If a sum of ₹5,000 doubles in 5 years at simple interest, what is the annual rate of interest?

दोगुना होने का अर्थ है ब्याज = मूलधन = ₹5,000। दर = (ब्याज * 100) / (P * T) = (5000 * 100) / (5000 * 5) = 100 / 5 = 20%।