Hello and welcome to Algebra Demystified! Today I’d like to tell you about a great mnemonic tool to remember the formulas of the area and circumference of a circle. As you know, I love mnemonics, and whenever I find a good one, I’m always posting it on my blog!
I’ll start by listing the two formulas and the legend of the symbols (what the letters mean in the formulas). Then I’ll tell you the (short) mnemonic phrases. I meant to build the suspense up to the end, but you may skip to the end if you’d like and work backwards.
C = πd
The legend goes as follows:
- C stands for the circumference,
- d stands for the diameter of the circle.
The diameter of a circle is the length of a line that you can draw between two points on the edge of a circle, provided you cross the center. You would do it like so:
And the formula for the area of a circle is:
A = πr2
The legend is:
- A is the area of the circle,
- r is the radius of the circle.
The radius is the distance from the center to any of the points on the edge. If you’d like a neater explanation, just take any of the halves of the diameter formed by the center. Both of those halves could be called a “radius”.
Now comes the mnemonic:
Cherry pies are delicious! Apple pies are too!
I left the most fun part for the end! Those two mnemonics stand for the two formulas I mentioned in this post. It’s better to remember them together, since they form a great logical blend.
Cherry (C) pies (π) are delicious (d)!
Apple (A) pies (π) are (r) too (2)!
There’s only one caveat to this mnemonic, which is not to mistake the “are” in the first sentence with a “r” in the formula. But remember, we never put radius and diameter together in any formula, since the radius and diameter of any circle can be expressed in terms of each other. In other words, if you know the radius, you can calculate the diameter by doubling the radius. And if you know the diameter, calculating the radius is no big deal: you simply divide by 2.
As always, suggestions, thanks, or just any comments are welcomed in the Comments section! Thanks and I hope that my blog post has helped you in some way! 🙂
Algebra Demystified 
Instead of “are” delicious, you could say “taste” delicious, thereby removing confusion of r=radius
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Thanks! Good idea, I’ll add it as soon as possible. 🙂
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It helped me with my homework!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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