Clearly it's 4 kyu...

Could you provide an example? Because I can't see how 2 versions with identical fixed/random tests and identical reference solutions can be different.

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v = d/t => d = v*t
check your code

AFAIK the test cases for this Kata do not specifically test against inefficient solutions so unless you deliberately come up with an extremely inefficient solution, all tests should be executed in around 2 seconds or so. Chances are that your solution doesn't handle [] properly and ends up in some sort of infinite loop.

If you still need further help, feel free to specify the language in which you are experiencing the problem and post your solution here (and mark it as a spoiler, of course) and I'll see if I can help :)

Thanks Chris_Rands for responding to the issue. Appreciate it! Closing issue.

Resubmitting slightly modified solution (one space is enough) usually helps.