The compound interest on ₹18,000 at 7% per annum, compounded annually, is ₹1,260. What is the period of time?

$$interest\ =\ principal\ amount\left[\left(1+\frac{Rate\ of\ interest}{100}\right)^{time}-1\right]$$

$$1260\ =\ 18000\left[\left(1+\frac{7}{100}\right)^{time}-1\right]$$

$$1260\ =\ 18000\left[\left(\frac{107}{100}\right)^{time}-1\right]$$

$$1260\ =\ 18000\left(\frac{107}{100}\right)^{time}-18000$$

$$1260+18000\ =\ 18000\left(\frac{107}{100}\right)^{time}$$

$$19260\ =\ 18000\left(\frac{107}{100}\right)^{time}$$

$$\frac{19260}{18000}\ =\left(\frac{107}{100}\right)^{time}$$

$$\frac{107}{100}\ =\left(\frac{107}{100}\right)^{time}$$

So time = 1 year