A cross section is a cube, 30 cm long. If the length is increased by 5 cm, then the surface area will be increased by 80 square cm. How many square cm is the surface area of the original cuboid?

A cross section is a cube, 30 cm long. If the length is increased by 5 cm, then the surface area will be increased by 80 square cm. How many square cm is the surface area of the original cuboid?

80 ﹣ 5 ﹣ 4 = 4cm (bottom edge length)
Surface area = 4 × 30 × 4 + 4 × 4 × 2 = 512 square cm