Two cars A and B are at $100\,\text{m}$ and $200\,\text{m}$ distance from the origin $O$ at time $t = 0$.

They start simultaneously with velocities $10\,\text{m/s}$ and $5\,\text{m/s}$ respectively. A will overtake B at a distance of $x$ from $O$.

The answer given: $300\,\text{m}$.

What I have tried so far: I tried to calculate the relative velocity of car A and then to find out the time and the distance but I got stuck. And each time I try, I go with a different approach, so, really, I haven't a clue even on how to proceed to solve this problem.


closed as off-topic by John Rennie, Ali, Brandon Enright, ACuriousMind, BMS Sep 3 '14 at 15:23

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  • $\begingroup$ "And each time I try, I go with a different approach" - That's an interesting observation. Have you tried to calm down and observe yourself why your reasoning is so chaotic? Some other people learn the art of self-control so every time they try, they may repeatedly use the same correct approach that they previously identified to be correct. $\endgroup$ – Luboš Motl Sep 3 '14 at 13:02

Probably there are many ways to approach the problem, The simplest, the first that comes to my mind is : find the time it takes.

Think of the time it takes A to cover/catch up the difference in space using the difference of speed.

P.S I hope this hint is not against the rule, if it is, just tell me and I delete my answer.


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