If the present value of perpetuity of ₹600 payable at the end of every six months is ₹18000, then the rate of interest is :

$\frac{20}{3}$ % per annum

The correct answer is Option (1) → $\frac{20}{3}$ % per annum

To find the rate of interest,

$PV=\frac{A}{r}$

$⇒r=\frac{A}{PV}=\frac{60}{18000}≃0.033$

∴ Annual rate = $0.033 × 2 = 0.066$

$≃6.66\%$