Running at an average rate of 6 meters per second a sprinter

Running at an average rate of 6 meters per second, a sprinter ran to the end of the track. The sprinter then jogged back to the starting point at an average rate of 3 meters per second. The total time for the sprint and the jog back was 2 minutes and 40 seconds. Find the length of the track.

2 minutes 40 seconds=160 seconds
6x=3(160-x)
x=160/3
6*160/3=2*160=320 meters long
check
6*160/3+3*(160-160/3)=640