Another athlete runs 8 laps every day on the same 400m running track. How many days will it take him to run a total of 100 km?
Well you have the required distance of 100 km. The runner is running 8 laps/day x 400 meters/ lap = 3200 meters/day. Then you need to see when this will amount to 100 km = 100 000 meters.
t days x 3200 meters/day = 3200 t meters = 100 000 meters. It should be straight forwards from now.