7) D

Total area of patio = 5 x 4 = 20 m²

Area of 1 big square tile = 0.6 x 0.6 = 0.36 m²
Number of big black tiles = 6
Total area of big black tiles = 6 x 0.36 = 2.16

Area of 1 small square tile = 0.4 x 0.4 = 0.16 m²
Number of small black tiles = 2
Total area of big black tiles = 2 x 0.16 = 0.32

Area of a rectangular tile = 0.4 x 0.6 = 0.24 m²
Number of small black tiles = 6
Total area of big black tiles = 6 x 0.24 = 1.44

Total black area = 1.44 + 2.16 + 0.32 = 3.92

Percentage of black area = (3.92 / 20) x 100 = 3.92 x 5 = 19.6%

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