Question: In a 1 km race, A wins B by 40 meters and A wins C by 70 meters (same race). Assuming that they run at constant speed, the distance by which B wins C in the race can be expressed in the form x/y , where x and y are coprime positive integers. Find xy. Original question is titled Are you smarter than a fifth grader- Part 5 by Krishna Ar Only 14% of those who attempted it got it right.
I wrote up a great solution explaining how you can approach such a problem, and motivated how to think about such questions. I would encourage you to read it, and then practice on a similar problem Only 28% who attempted it got it right.