If Rs.2000 amounts to Rs.2500 in 2 years at simple interest, what is the rate of interest per annum?
8%
37.5%
25%
12.5%
$\begin{aligned} & \mathrm{I}=\mathrm{A}-\mathrm{P} \\ & =2500-2000=500 \\ & 500 / 2000 \times 100=25 \% \\ & \text { Interest for } 2 \text { years }=25 \% \\ & \text { Interest for } 1 \text { years }=25 \% / 2=12.5 \%\end{aligned}$