Under this method, a fixed percentage of diminishing value of the asset is written off each year.   The annual charges of the depreciation decrease from year to year.

Written Down Value (WDV) = (Acquisition Cost – Depreciation)
Depreciation =  WDV * Depr Rate

RBM: The main advantage of this method is that total charge to total revenue is uniform when the depreciation is high, repairs are negligible and as the repairs increases the burden of depreciation gets lesser and lesser.

RBM:

For First Year Depreciation = Acquisition  value * Rate
For Second Year on words    
Depreciation = Written down    value * Rate