wrote the exam last year and had to do a sup. calculator not needed, cant remember if they did not allow calculators to be used, but i took one along just in case.
in both exams there was no question where we had to do the whole log 2 stuff.
The exam tutorial has questions on the decision trees and although there is an appendix A that eliminates the need for log 2 calculations there is still plenty of fractions to deal with.