Let the principal = ₹ 100
Amount = ₹ 200 – ₹ 100 = ₹ 100
Rate = 6 \frac{1}{4} %
∴ Time = \frac{\text { Interest } × 100}{\text { Principal } × \text { Rate }}
= \frac{100 × 100}{100 × \frac{25}{4}}
= \frac{100 × 4}{25} = 16 years
∴ Required time = 16 years