Rectangle = l × w
Triangle = ½ b h
Circle = πr²
Circumference = 2πr
Sector = (θ/360)πr²
Arc = (θ/360)2πr
Cuboid V = lwh
Cuboid SA = 2(lw+lh+wh)
Cylinder V = πr²h
Curved = 2πrh
Cone V = ⅓πr²h · curved = πrl
Sphere V = (4/3)πr³ · SA = 4πr²
Hemisphere V = (2/3)πr³
Double shape = add the volumes
Empty space = big − small
Recast: volume stays the same → V₁ = V₂
Water rise = volume dropped in