All the multi engine jets that I've flown are definitely in the 85-90% RPM band with the possible exception of the Vulcan which was so overpowered that long range cruise power, as I recall, was slightly less ;-) Of course the person that set the question may live in the theoretical rather than the real world, however my ' Boys Book of Aeroplanes'(AP3456) states that turbojet aircraft cruise using approx 90% of max thrust for the best range.
Last edited by Specaircrew; 17th Aug 2021 at 21:34.