2021 Fall AMC 10A Problems/Problem 3

Problem

What is the maximum number of balls of clay of radius $2$ that can completely fit inside a cube of side length $6$ assuming the balls can be reshaped but not compressed before they are packed in the cube?

$\textbf{(A) }3\qquad\textbf{(B) }4\qquad\textbf{(C) }5\qquad\textbf{(D) }6\qquad\textbf{(E) }7$

Solution

A sphere with radius $2$ has volume $\frac {32\pi}{3}$ . A cube with side length $6$ has volume $216$ . If $\pi$ was $3$ , it would fit 6.75 times inside. Since $\pi$ is approximately $5$ % larger than $3$ , it is safe to assume that the $3$ balls of clay can fit $6$ times inside. Therefore, our answer is $\boxed {(D)6}$ .

~Arcticturn

2021 Fall AMC 10A (Problems • Answer Key • Resources)
Preceded by Problem 2	Followed by Problem 4
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2021 Fall AMC 10A Problems/Problem 3

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