The price of a commodity which was Rs. 250 three years ago is Rs. 2000 now. The annual rate of increase in the price is ?

$$\eqalign{ & \Rightarrow 250{\left( {1 + \frac{R}{{100}}} \right)^3} = 2000 \cr & \Rightarrow {\left( {1 + \frac{R}{{100}}} \right)^3} = \frac{{2000}}{{250}} \cr & \Rightarrow {\left( {1 + \frac{R}{{100}}} \right)^3} = 8 = {\left( 2 \right)^3} \cr & \Rightarrow \left( {1 + \frac{R}{{100}}} \right) = 2 \cr & \Rightarrow \frac{R}{{100}} = 1 \cr & \Rightarrow R = 100 \% \cr} $$