# Algebra formulas for ACT

## 30 terms

### Averages

A= x1 + x2 + x3 / n

is/of = %/100

### Price Percentage Change

delta% = New price - old price / old price

### Distance Problems

Distance = Rate x Time

### Combined work rate problems

Rate 3 = Rate 1 + Rate 2

### Simple interest problems

Interest = Principal x Rate x time

### Compound interest Problems

Interest = (Principal)(1 + Rate) ^# of periods - Principal

### Slope of a line

m = y2 - y1 / x2 - x1

### Perimeter of a square

P square = 4s; s = sides

### Perimeter of a rectangle

P rectangle = 2l + 2w; l = length w = width

### Perimeter of a triangle

P triangle = a + b + c; a, b, and c are the sides

### Circumference of a circle

C circle = 2pi x r; pi = 3.14, r = radius

### Area of a square

A square = s^2, s = length of side

### Area of a rectangle

A rectangle = lw; l= length, w = width

### Area of a parallelogram

A parallelogram = bh; b = base, h = height

### Area of a trapezoid

A trapezoid = (b1 + b2)h / 2; b = base, h = height

### Area of a triangle

A trianngle = bh / 2; b= base, h = height

### Area of a circle

A circle = pi x r^2; r = radius, pi = 3.41

### Volume of a circle

V cube = s^3; s= side

### Volume of a rectangle solid

V solid = lwh; l = length, w = width, h = height

### Volume of cylinder

V cylinder = pi x r^2 x h; h = height, r = radius

### Volume of a cone

V cone = pi x r^3 x h / 3

### Surface area of a sphere

A sphere surface = 4 x pi x r^2

### Volume of a sphere

V sphere = 4 x pi x r^3 / 3

### Real numbers

Are all the numbers on the number line, including integers, decimals, fractions, and radical numbers

### Natural numbers

Are the set of positive integers and are referred to as counting numbers

### Whole numbers

Are the numbers used for counting plus the number zero

### Integers

Positive or numbers whole numbers

### Median

The middle value of a number set when arranged in ascending order.

### Mode

The value that appears the most often in a set of numbers