If a car going at 50 kmph North, then turns West and the speed remains unchanged, can you find the speed while turning?
If the speed remains unchanged, then the car must have turned (from North direction to West direction, that is, towards left) at the speed of 50 kmph.
In general, we slow down our vehicles, when taking a turn. The decrease in our speed is, in general, proportional to the steepness of the turn, our current speed, type of vehicle, etc. When taking a right angle turn (as in this case, from north to west), we typically slow down a lot. When taking a blind turn (for example, on mountains, etc.), we ideally slow down to very low speeds. Here, we are not given any other information than that the car's speed remains unchanged. In such a scenario, we have to assume that the car must have taken the turn at the speed at which it was traveling before taking the turn.
Hope this helps.