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2025 AMC 8 Problems/Problem 8: Difference between revisions

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== Problem ==


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 <imath>18</imath> square centimeters. What is the volume of the cube in cubic centimeters?
[[File:Amc8_2025_prob8.PNG]]
<imath>\textbf{(A)}~3\sqrt{3} \qquad \textbf{(B)}~6 \qquad \textbf{(C)}~9 \qquad \textbf{(D)}~6\sqrt{3} \qquad \textbf{(E)}~9\sqrt{3}</imath>
== Solution 1 ==
Each of the <imath>6</imath> faces of the cube have equal area, so the area of each face is equal to <imath>\frac{18}{6} = 3</imath>, making the side length <imath>\sqrt3</imath>. From this, we can see that the volume of the cube is <imath>\sqrt{3}^3 = \boxed{\textbf{(A)}~3\sqrt{3}}</imath>
~Sigmacuber
== Solution 2 ==
Let the side length of the cube shown be equal to <math>s</math> centimeters. The surface area of this cube is equal to the area of the net of the cube, which is equal to <math>18</math> square centimeters. The surface area of this cube is also <math>6s^2</math> square centimeters, so we have
<cmath>6s^2 = 18 \implies s^2 = \frac{18}{6} = 3 \implies s = \sqrt{3}.</cmath>
However, we aren't done. We have found that the side length of the cube is <math>\sqrt{3} cm</math>, but the question asks for the volume of the cube, which is equal to <math>s^3 = \sqrt{3}^3 = \boxed{\textbf{(A)}~3\sqrt{3}}</math> cubic centimeters.
~[[User:aoum|aoum]]
== Video Solution 1 by Cool Math Problems ==
https://youtu.be/BRnILzqVwHk?si=h0-bM3iwNbCG0cm-&t=253
== Video Solution 2 by SpreadTheMathLove ==
https://www.youtube.com/watch?v=jTTcscvcQmI
== Video Solution 3 ==
[//youtu.be/VP7g-s8akMY?si=UuALQxA6xGUGW8hN&t=577 ~hsnacademy]
== Video Solution 4 by Thinking Feet ==
https://youtu.be/PKMpTS6b988
==Video Solution(Quick, fast, easy!)==
https://youtu.be/fdG7EDW_7xk
~MC
== See Also ==
{{AMC8 box|year=2025|num-b=7|num-a=9}}
{{MAA Notice}}
[[Category:Introductory Geometry Problems]]

Latest revision as of 14:48, 10 November 2025

Problem

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?

$\textbf{(A)}~3\sqrt{3} \qquad \textbf{(B)}~6 \qquad \textbf{(C)}~9 \qquad \textbf{(D)}~6\sqrt{3} \qquad \textbf{(E)}~9\sqrt{3}$

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 $\sqrt{3}^3 = \boxed{\textbf{(A)}~3\sqrt{3}}$

~Sigmacuber

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.

~aoum

Video Solution 1 by Cool Math Problems

https://youtu.be/BRnILzqVwHk?si=h0-bM3iwNbCG0cm-&t=253

Video Solution 2 by SpreadTheMathLove

https://www.youtube.com/watch?v=jTTcscvcQmI

Video Solution 3

~hsnacademy

Video Solution 4 by Thinking Feet

https://youtu.be/PKMpTS6b988

Video Solution(Quick, fast, easy!)

https://youtu.be/fdG7EDW_7xk

~MC

See Also

2025 AMC 8 (ProblemsAnswer KeyResources)
Preceded by
Problem 7
Followed by
Problem 9
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AJHSME/AMC 8 Problems and Solutions

These problems are copyrighted © by the Mathematical Association of America.