Barometric pressure?

Question

CH 2, 56) An aircraft is standing on an airfield 220ft above sea-level on a day when the barometric pressure at ground level is 1004mb. If the pilot sets the altimeter to read 220ft on this day, what will it read if the barometric pressure drops to 992mb.

Answer 1

A quick rule of thumb is that atmospheric air pressure declines 1 mb for every 33 ft increase in altitude.  If the pressure declines from 1004 mb to 992 mb , i.e. 12 mb, the altimeter would register an increase in altitude of 12x33 = 396 ft, which when added to the current setting of 220 ft (for 1004 mb) would give an erroneous reading of 616 ft.