Three runners, Dirk, Edith, and Foley all start at the same time for a $24$ km race, and each of them runs at a constant speed. When Dirk finishes the race, Edith is $10$ km behind, and Foley is $15$ km behind. When Edith finishes the race, how far behind is Foley, in km?
Let's find how far everyone ran when Dirk finished.
When Dirk finishes, Edith has ran 14km while Foley has only ran 9km.
This means that Foley runs only 9/14 as fast as Edith.
We can now find how far Foley ran when Edith finished the race.
Plugging in 24, we find that Foley has only ran \(24 (9/14) ≈ 15.43 km\) when Edith ran 24.
This means Foley was \(24 - 15.43 ≈ 8.57\)km behind Edith.
So our final answer is 8.57km.
Thanks! :)