your fertilizer spreader covers a swath with a width of 50 f

your fertilizer spreader covers a swath with a width of 50 feet. after disengaging the driven chain. a container was attached to the delivery chute and the spreader containing 15-15-15 is driven for 100 feet. the contents off the container are weighed and found to be 39lb. what is the N application rate in pounds per acre

Solution

The fertilizer spreader has applied 39 lbs of 15-15-15 fertilizer over an area of 50*100 = 5000 sq.ft. Since 1 acre = 43,560 sq. ft, hence 39 lbs of 15-15-15 fertilizer was applied over an area of 500/43560 = 0.114784205 acre. Further, the 15-15-15 fertilizer contains 15 % N. Hence, 39 lbs of 15-15-15 fertilizer contains 39*15/100 = 5.85 lbs of N. Thus, 5.85 lbs of N was applied over 0.114784205 acre. Therefore, the N application rate in pounds per acre is 5.85/0.114784205 = 50.97 lbs per acre approximately ( on rounding off to 2 decimal places).