TITLE: Does this pattern continue $\lfloor\sqrt{44}\rfloor=6, \lfloor\sqrt{4444}\rfloor=66,\dots$?
QUESTION [44 upvotes]: By observing the following I have a feeling that the pattern continues.
$$\lfloor \sqrt{44} \rfloor=6$$
$$\lfloor \sqrt{4444} \rfloor=66$$
$$\lfloor \sqrt{444444} \rfloor=666$$
$$\lfloor \sqrt{44444444} \rfloor=6666$$
But I'm unable to prove it. Your help will be appreciated.

REPLY [6 votes]: This can be proved a bit more simple.
The general term can be written as $4 \frac{10^{2n} - 1}{9}$. Taking square root will give you $\frac{2}{3} \sqrt{10^{2n} - 1}$. As $\frac{2}{3} \approx 0.66666666666$ and $\sqrt{10^{2n} - 1} \approx \sqrt{10^{2n}} = 10^n$, this explains why the result is $6;66;666;...$ etc. To prove rigorously, observe that: $66...66 = \frac{2}{3} 10^n - \frac{2}{3} < \frac{2}{3} \sqrt{10^{2n} - 1} < \frac{2}{3} 10^n = 66...66.67$.