2025 AMC 8

Complete problem set with solutions and individual problem pages

Problem 8 Easy

Isaiah cuts open a cardboard cube along some of its edges to form the flat shape shown on the right, which has an area of 18 square centimeters. What is the volume of the cube in cubic centimeters?

  • A.

    3\sqrt{3}

  • B.

    6

  • C.

    9

  • D.

    6\sqrt{3}

  • E.

    9\sqrt{3}

Answer:A

Solution 1

Each of the 6 faces of the cube have equal area, so the area of each face is equal to \frac{18}{6} = 3, making the side length \sqrt3. From this, we can see that the volume of the cube is \sqrt{3}^3 = \boxed{\textbf{(A)}~3\sqrt{3}}

 

Solution 2

Let the side length of the cube shown be equal to s centimeters. The surface area of this cube is equal to the area of the net of the cube, which is equal to 18 square centimeters. The surface area of this cube is also 6s^2 square centimeters, so we have

6s^2 = 18 \implies s^2 = \frac{18}{6} = 3 \implies s = \sqrt{3}.

However, we aren't done. We have found that the side length of the cube is \sqrt{3} cm, but the question asks for the volume of the cube, which is equal to s^3 = \sqrt{3}^3 = \boxed{\textbf{(A)}~3\sqrt{3}} cubic centimeters.