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Old 05-15-2017, 05:14 PM
Fiendish Astronaut Fiendish Astronaut is offline
Join Date: Jan 2001
Location: London - England
Posts: 1,039
The electronic calculator. You can get a solar powered one for a dollar and they'll last a life time giving you accurate calculations that only a few generations ago would have been hugely complicated and time consuming for a single person to perform.