To determine by how many meters A beats C, we first need to analyze the relationships based on their speeds and time taken. Given:
We can express time as distance/speed. Since all runners run at uniform speeds for the same amount of race time:
We want to find how much distance C covers in the time A finishes 10 km:
A beats C by the difference between 10 km and 8.1 km:
The correct answer is thus: 1900 meters.
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: