Question

7 2. A big cube of side 9cm is formed by rearranging together 81 small but identical cubes each of side 3cm. further, if the corner cubes in the topmost layer of the big cube are removed, what is the change in to- tal surface area of the big cube ? ​

Answer 1

Answer:

After removing the corner cubes in the topmost layer , 108cm^2 surface decrease from previous total surface of the big cube and the remaining total surface of the big cube be 378 cm^2

Step-by-step explanation:

Surface of one side of the big cube of side 9 cm is 9^2 cm^2 = 81 cm^2to

total surface of the big cube = 6×81 = 486 cm^2

surface of one side of a small cube of side 3cm is = 3^2 cm^2 = 9 cm^2  

total surface of 3 side of a small cube is 3×9 = 27 cm^2

there are total 4 small cubes in the topmost layer of the big cube

change in total surface are of the big cube = 4 × 27 cm^2 = 108 cm^2

after removing the corner cubes in the topmost layer remaining total surface of the big cube is 486- 108 = 378 cm^2