The sides of triangular pieces are 20 cm, 50 cm and 50 cm. Let, a = 20 cm, b = 50 cm, c = 50 cm ∴ Semi-perimeter, s = (a + b + c)/2 = (20 + 50 + 50)/2 s = 60 cm ∴ Area of one triangular piece = root under ( √s(s - a)(s - b)(s - c) = root under ( √60(60 - 20) (60 - 50) (60 - 50) = root under ( √60 x 40 x 10 x 10) = 200 √6cm2 Cloth of each design required for one umbrella = Area of 5 triangular pieces = 5 x 200 √6 = 1000 √6 cm2 Cloth of each design required for 20 umbrellas = 20 x 1000 √6 = 20,000 √6 cm2 Helpful, caring, loving.