
From right triangle \( \triangle APB \):
Using the Pythagorean Theorem:
\[
AP^2 = AB^2 - BP^2
\]
Given: \( AB = 10 \), \( BP = 6 \)
\[
AP^2 = 10^2 - 6^2 = 100 - 36 = 64 \Rightarrow AP = \sqrt{64} = 8
\]
Since AP = 2x, we get:
\[
2x = 8 \Rightarrow x = 4
\]
So, \( AQ = x = 4 \)
Now from right triangle \( \triangle AQB \):
Again using the Pythagorean Theorem:
\[
BQ^2 = AB^2 - AQ^2 = 10^2 - 4^2 = 100 - 16 = 84
\]
So:
\[
BQ = \sqrt{84} \approx 9.17
\]
Answer: \( \boxed{BQ = \sqrt{84} \approx 9.17} \)

For any natural number $k$, let $a_k = 3^k$. The smallest natural number $m$ for which \[ (a_1)^1 \times (a_2)^2 \times \dots \times (a_{20})^{20} \;<\; a_{21} \times a_{22} \times \dots \times a_{20+m} \] is: