I must have the algebra wrong somewhere but here is the original equation:
$$\frac{152e}{180n^4}<.0001$$
If I then multiply like this:
$$152e<.0001(180)n^4$$
Which then gives:
$$152e < .0018n^4$$
And then dividing:
$$\frac{152e}{.0018} < n^4$$
And then taking the fourth root:
$$\sqrt[4]{\frac{152e}{.0018}}< \sqrt[4]{n^4}$$
And I get about $n = 46.338$
But the book gives a solution of $14$. Can someone explain where I went wrong?
$\dfrac{152 \mathrm{e}}{180n^4}<0.0001$
$152 \mathrm{e} < 0.018n^4$
$\dfrac{152 \mathrm{e} }{0.018} < n^4$
$n > \sqrt[4]{22954.38}$
$n > 12.31$
This still doesn't explain why the solution is listed as $14$, though.