Annual depreciation of fixed assets = depreciated fixed assets/estimated service life of fixed assets =500/5= 100.
Monthly depreciation of fixed assets = annual depreciation/12 =100/12 = 8.33.
Depreciation rate of fixed assets = annual depreciation of fixed assets/original value of fixed assets = 100/500=20%.
The straight-line depreciation method, also known as the average life method, refers to a method of calculating the depreciation of fixed assets on average according to the expected service life and distributing it to each period on average. The depreciation of each period (year, month) calculated by this method is equal.