If a solid sphere is cut into two equal hemispheres, by what percentage is the total surface area increased?

Surface area of sphere = 4πr². Each hemisphere has curved surface area = 2πr² plus a flat circular base = πr², total per hemisphere = 3πr². Two hemispheres total = 6πr². Increase = 6πr²-4πr² = 2πr². Percentage increase = (2πr²/4πr²)×100 = 50%.