Farmer Alice has a farm that consists of 5 acres of apples, 10 acres of oranges, and 15 acres of grapes. Apples require 30 gallons of water per acre, oranges require 50 gallons of water per acre, and grapes require 60 gallons of water per acre. What fraction of the total water used on the farm is used for irrigating the grapes? Additionally, express this fraction as a percentage. Let's think step by step and output the final answer within \boxed{}.
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