You can go approximately 1/4 mile before the phone will start to get fuzzy and then drop the call.
It has a range of 5 meters I beleive.
A 150 grain bullet shot from a 308 will start dropping the fraction of a second it leaves the barrel.
You can be up to 60 feet away from the phone.
Because cordless telephones are communicating to the base unit through a signal. So if you get a call, your base unit will direct the call to the cordless device. If the cordless device can't receive a signal from the base unit, it will stop working.
Most cordless phones will allow users to talk up to 100 feet away from the base without degredation.
60 feet
far
60 feet
Unless the number happens to be a straightforward power of the base of the logs, the answer is that you cannot without some access to tables or a scientific calculator. There are Maclaurin series for the log function but without a powerful calculator, you will not get far with them.
Call Of Duty by far
70 feet
127 feet