## Math Help: Helpful Math Formulas

Having these formulas ready in mind will help as you advance through your math career.

### Average/Mean

Remember that the average is the same as the mean. To find the average of a set of numbers, divide the sum of all the numbers in the set by the amount of numbers in the set.

### Percentages

To find

x percent of a number (

n),

To find what percent a number (

n) is of another number (

m),

And finally,

n is

x percentage of what number?

### Circle Formulas

The area of a circle is the square of the radius times π.

Multiply π times the diameter, or twice the radius, of a circle.
When working with arcs, just remember that an arc is a percentage of a circle. Since there are 360 degrees in a circle, first calculate the percentage of the whole circle the arc represents. If the arc is 90 degrees, it is 90/360=1/4 or 25%. Multiply the area or circumference of the whole circle by this percentage to find the area or circumference of the arc.

### Cylinder Volume

The volume of a cylinder is the area of the circle that makes up its end times the height of the cylinder.

### Pythagorean Theorem

For any right triangle, the length of the hypotenuse (

c) squared is equal to the sum of the squares of the two shorter sides (

a and

b).

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