Mega quick way to work out reciprocals
Using the first 2 digits, take 2 from digit 1, and add to digit 2, or vice versa.
eg
Heading 035 becomes 215
Heading 218 becomes 038
Heading 149 becomes 329
Doesn't always work as your answer may take you above 360, however easy to correct if it does.
That concludes our lesson for today. Happy flying to all you cloud bunnies