Using Pythagoras theorem ⇒ (20√2)2=x2+x2 ⇒ 800 = 2x2 ⇒ 400 = x2 ⇒ x = 4√00 = 20 cm ∴ Area of a square = x2=202=400cm2 ∴ Perimeter of a square = 4x = 4 x 20 = 80 cm
