Explanation
Correct answer: B.
Choice B is correct. A cube has 6 faces of equal area, so if the total surface area of a cube is , then the area of one face is . Likewise, the area of one face of a cube is the square of one of its edges; therefore, if the area of one face is , then the length of one edge of the cube is . Since the perimeter of one face of a cube is four times the length of one edge, the perimeter is .
Desmos solution:
Note: The black line shows P - a = 0, so the perimeter P equals a.
Enter in Desmos:
Reviewed and rewritten by CookSAT
Why the other choices are wrong
Choice A
Choice A is incorrect because if the perimeter of one face of the cube is , then the total surface area of the cube is , which is not .
Choice C
Choice C is incorrect because if the perimeter of one face of the cube is , then the total surface area of the cube is , which is not .
Choice D
Choice D is incorrect because if the perimeter of one face of the cube is , then the total surface area of the cube is , which is not .
Student discussion
getcooksat 0 likes
The surface area of the cube is 6(b/4)^2, so the area of one side of the cube is (b/4)^2. Also, this means that one side length of the cube is b/4. Since we're finding the perimeter of one face of the cube, we can solve for it by doing (b/4)*4.