FirstDorhnPilot,
Someone has mentioned the 1 in 60 rule earlier, which is useful for in-flight nav computations, but one trick that I don't think has been mentioned yet, and is REALLY useful, is how to calculate a reciprocal bearing.
If the bearing is less than 200, add 200 and subtract 20.
If the bearing is 200 or more, subtract 200 and add 20.
For example, if the runway in use is say 24 and you need to know the downwind leg heading, you could scrabble around looking for the airfield plate to find the runway number for the other end of 24 or you could mentally do this:
Runway 24 = 240. 240 - 200 = 040. 040 + 20 = 060
Note: this method will give numbers larger than 360 for headings in the range 180 to 199, so then you need to make an adjustment.
Alternatively, use 180 as the break between adding and subtracting 200. Use whichever method you find easier.
Good luck. As everyone has said, not much mathematics is required. Just remember that your first priority is to fly the aeroplane. When you're moving at two miles per minute, it is easy to get mentally "behind the aeroplane" if you are concentrating on doing maths.
I've often found that when I notice I'm off track (and not flying with an instructor or examiner
), "left a bit" or "right a bit" works very well.