Handy Formulas
“Never memorize anything you can read out of a book.” –Albert Einstein
Here are many handy formulas for those of us who take Einstein far too seriously.
At least, that’s my excuse for never memorizing most of the following.
Terminology:
p the symbol for its ratio [ p = circumference ¸ diameter ] It is represented as 3.1416.
¸ operation, divide
´ , · operation, multiply
Ö square root
a = area, a measure of the size of its surface. Areas are measured in square units.
b = breadth of base.
h = perpendicular height.
l = length of base.
p = perimeter of a plane figure is the distance around its edge or boundary. This is measured in linear units.
r = length of radius.
t = length of top.
v = volume of a solid figure is a measure of the amount of space it occupies. This is measured in cubic units.
Formulas for Perimeters
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Circle |
p = 2 ´ p ´ r |
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Rectangle |
p = 2 ( b + h ) |
Formulas for Area
|
Circle |
a = p ´ r2 |
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Rectangle, Parallelogram |
a = b ´ h |
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Triangle |
a = ½ ´ b ´ h |
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Trapezium |
a = ((a + b) h) / 2 |
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Cube (or cubelike object) |
a = h ´ b ´ 6 |
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Prism |
a = (b ´ h) + (3 ´ l ´ b) |
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Cylinder |
a = (2 ´ p ´ r ´ l) + (2 ´ p ´ r2) |
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Pyramid |
a = (2 ´ b ´ h) + (b2) |
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Sphere |
a = 4 ´ p ´ r2 |
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Formulas for Volume
|
Cone |
v = (p ´ r2 ´ h) / 3 |
|
Cube or cubelike object |
v = b ´ h ´ l |
|
Cylinder |
v = p ´ r2 ´ l |
|
Prism |
v = (b ´ h ´ l) / 2 |
|
Pyramid |
v = (b ´ h ´ l) / 3 |
|
Sphere |
v = (4 ´ p ´ r3) / 3 |
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Decimal Equivalents
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Avoirdupois Apothecaries |
Troy Solid (or cubic) Paper |
Time
60 seconds make 1 minute
60 minutes makes 1 hour
24 houres make 1 day
7 days make 1 week
4 weeks make 1 month
52 weeks make 1 year
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Long Measure Coal Measure |
Cloth Measure Dry Measure |
Wine Measure Ale and Beer |
Land Measure
9 feet make 1 yard
30¼ yards make 1 pole
40 poles make 1 rod
4 rods make 1 acre
Conversions
Linear Conversions
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Converting Inches & Centimeters
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Converting Feet & Meters
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Converting Yards & Meters
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Converting Miles & Kilometers
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Use these to convert distance measurements from system to system.
Also, note nautical miles (knots) are different than land measured miles.
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Units |
Approx |
Accurate |
|
knots ® miles |
´ 1.2 |
´ 1.15 |
|
miles ® knots |
¸ 1.2 |
¸ 1.15 |
Area Conversions
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Converting Inches & Centimeters
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Converting Feet & Meters
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Converting Yards & Meters
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Converting Miles & Kilometers
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Use these to convert surface area measurements from system to system.
Volume Conversions
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Converting Inches & Centimeters
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Converting Feet & Meters
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Converting Yards & Meters
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Converting Miles & Kilometers
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Use these to convert cubic measurements from system to system.
Other Conversions
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Converting Gallons & Liters
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A final note on this topic, a liter is 1000 cubic centimeters in displacement.
