Math 101	Intermediate Algebra
Formulas Chapter 2, Section 2 Formulas A formula is a general representation of an equation (or relationship). A formula will have many variables and few specific numbers in it. Example:   v = d t is a formula for speed where v is the speed, d is the distance, and t is the time. Evaluating Formulas Given:  the formula. Given:  values for all but one variable. Goal:  determine the value of the unknown variable for the given variable values. Example:  evaluate v = d t when d = 300 miles and t = 5 hours. Answer: v = 300 miles   5  hours  = 60 mph. Solving for One Variable of a Formula Given:  the formula. Asked to:  solve for a particular variable. Goal:  isolate the particular variable on the left hand side with everything else on the right hand side. Example:  given v = d t solve for t. Answer: t = d v Subscripts Subscripts are smaller numbers or letters placed to the lower right of letters. Formulas often contain variables with subscripts. Examples x1 is read "x sub 1" and 1 is the subscript. Rk is read "R sub k" and k is the subscript. Some Greek Letters (and Common Meanings) Greek letters are often used in formulas. Some greek letters have meanings that are usually associated with them. Letter Meaning (small pi) a constant (see to 1000 places) (small theta) an angle (capital sigma) summation of many (capital pi) product of many Some Common Formulas Formula Use A = r2 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 A = 1 2 BH Area of a triangle. B is base length, H is height a2 + b2 = c2 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 A = P(1 + r n ) nt 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 C = 5 9 (F - 32) Temperature conversion. F is degrees Fahrenheit C is degrees Centigrade