Simple interest is calculated on the original principal only, so it is the same every year.
1Formulas
SI = (P × R × T)/100
P = (100 × SI)/(R × T), R = (100 × SI)/(P × T), T = (100 × SI)/(P × R)
Amount A = P + SI
2Useful results
A sum doubles in 100/R years
If a sum amounts to A₁ in t₁ years and A₂ in t₂ years, SI per year = (A₂ − A₁)/(t₂ − t₁)