So in for your original question "how far will I go at 98 kts in 2 1/2 mins" I would do the quick mental calculation as follows.

I'm still trying to work out the real world case for wanting to do such a sum.

I can see it the other way around - "at 98 knots how long will it take to go four miles" is part of answering the "report your estimate for the beacon" question.