Years ago I came up with this method to easily figure out the 4th and 5th of any note without having to write anything down. This will help you with the circle of 5ths as well as anytime you need to quickly determine the 4th or 5th.
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Please watch: "Guitar Neck Shootout: Fender vs Squier vs Mighty Mite"
https://www.youtube.com/watch?v=DgZgtRhcSIc
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