Useful life assumption

Hi All

As I do practice examples for F3, I have come across this issue of useful life assumption a couple of times.

The question will state that the NCA (usually land) has been revalued to a higher amount, it states the depreciation percentage and finally, it says that there is no change to the useful life after the revaluation.
I understand all of the above no problem, but after fighting with this question for a while and then getting the wrong answer, I discover that the useful life was originally 50 years! I didn’t see 50 years in the question…
I have come across this type of question a couple of times.

For exam purposes, do we automatically assume a useful life of 50 years if it is not mentioned in the question??