on April 1, 2002, the pacific landscaping company purchased a new lawnmower for $25,000. The lawnmower has an estimated life of four years and a $5,000 salvage value. Pacific landscaping uses the straight-line method of depreciation. Total depreciation expense for the year ended December 31, 2002, is

Take the cost less the salvage value divided by number of years to get the yearly amount of depreciaton.

But 2002 is a partial year, therefore you take the yearly amount times the number of months divided by 12 months (9/12 months) to get your depreciation expense for year 2002 because you had the asset for 9 months in the year.