That's just to make sure the student is paying attention. Apparently there are several answers given in units which might trap the unwary, be prepared to convert answers to different units/times.
I think this is justified where we commonly have have American training aircraft with a POH in lbs, statute mph and US Gallons yet we dispense fuel in litres and the CAA quote MTOM on G-INFO in Kg. We also refer to vertical distances in feet, short horizontal distances in metres/kilometres (runway lengths/visibility) and long navigational distances in Nautical Miles.
If a student isn't adept at being agile with all these units (and the use of the whizz wheel to resolve them all) they're going to come a cropper out there.
Remember the Gimli Glider
TOO