To find out how long it will take the athlete to run round the track fifteen times, we first know that it takes the athlete 58 seconds to complete one lap.
Now, we can calculate the time for fifteen laps:
\[ \text{Time for 15 laps} = 15 \times 58 \text{ seconds} \]
Calculating this:
\[ 15 \times 58 = 870 \text{ seconds} \]
Therefore, it will take the athlete 870 seconds to run round the track fifteen times.