Randy has a cube with an edge of 21 cm. From one corner of this cube Randy cuts and removes a cube with an edge of 15 cm. Find the percentage change in surface area of the original cube.
Original surface area 21 x 21 x 6 sides =2646 cm^2
New surface area 21 x 21 x 3 sides + 15x15x3 + (21 x 21 - (15x15) ) x 3
1323 + 675 + 648
No change in surface area
Thanks, EP.....to see this more clearly.....note that the cube that is removed had three exposed sides contributing to the original surface area of the original cube
But...note when the smaller cube is removed....the same surface areas remain on the altered cube