Yes order in floats operations can give different results so I gave an indication:

With floats it can happen that results depends on the operations order. To calculate hourly speed you can use:

(3600 * delta_distance) / s

Anyway nothing can't be modified now since more than 500 guys passed the C++ translation.

Indeed. As an example and possible non-spoiler hint,

(3600 * delta_distance) / s

can produce "correct" results while

3600 * (delta_distance / s)

can fail tests.

What a shame. The tests are disastrously bad. I eventually gave up, only to find the "top" C++ solution was almost line for line the same as mine. The difference comes only from rounding differences due to floating point inaccuracies.

You likely forgot to account for the case of an empty array of distances being passed.