Formula

Use

A = r^{2} 
Area of a circle. r is the radius 
C = 2r 
Circumference of a circle. r is the radius 
A = LW 
Area of a rectangle. L is length, W is width 
P = 2L + 2W 
Perimeter of a rectangle. L is length, W is width 

Area of a triangle. B is base length, H is height 
a^{2} + b^{2} = c^{2} 
Pythagoean theorem for a right triangle. a, b lengths of legs
c length of hypotenuse 
A = Prt 
Simple interest. A is interest earned, P is the principal, r is the interest rate (decimal), t is time 

Compound interest. A is interest earned, P is principal, r is interest rate (decimal),
n is number of times interest is paid per year,
t is time in years 
A = Rt 
Rates. A is amount, R is rate, t is time 
d = vt 
Distance and speed. d is distance, v is speed, t is time 

Temperature conversion. F is degrees Fahrenheit
C is degrees Centigrade 