First find the area of the painting: 2 feet * 4 feet = <<2*4=8>>8 square feet
Then find the area of the wall: 5 feet * 10 feet = <<5*10=50>>50 square feet
Then divide the area of the painting by the area of the wall and multiply by 100% to express the answer as a percentage: 8 square feet / 50 square feet * 100% = 16%
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