Chapter 1 – Tools of Algebra 1.5 – Rewriting Equations and Formulas

In this section we will review: Rewriting common formulas and equations that have more than one variable

1.5 – Rewriting Equations and Formulas When an equation has more than one variable, you can solve for ANY of the variables.

1.5 – Rewriting Equations and Formulas Common formulas Distance d = rt d = distance, r = rate, t = time Simple Interest I = Prt I = interest, P = principle, r = rate, t = time

1.5 – Rewriting Equations and Formulas Common formulas Temperature F = 9/5 C + 32 F = degrees Fahrenheit, C = degrees Celsius

1.5 – Rewriting Equations and Formulas Geometry Formulas Rectangle Perimeter P = 2l + 2w Area A = lw Triangle Perimeter P = a + b + c Area A = ½ bh

1.5 – Rewriting Equations and Formulas Geometry Formulas Trapezoid Area A = ½ (b 1 + b 2 )h Circle Circumference C = πd or C = 2πr Area A = πr 2

1.5 – Rewriting Equations and Formulas Example 1 Solve the formula F = ma for a.

1.5 – Rewriting Equations and Formulas Example 2 Solve the formula PE = mgh for h.

1.5 – Rewriting Equations and Formulas Example 3 A conservationist wants to survey a circular lake but cannot measure the diameter of the lake directly. Instead, the conservationist measures the circumference. It is 2 1/3 miles. What is the diameter of the lake, to the nearest ¼ mile?

1.5 – Rewriting Equations and Formulas Example 4 Find the value of y in the equation 3x + 4y = 10 when x = -2 and when x = 6.

1.5 – Rewriting Equations and Formulas Example 5 A campus bookstore sells T-shirts for $15 each and sweatshirts for $22 each. Write an equation with more than one variable for the bookstore’s revenue R from selling m T- shirts and n sweatshirts.

1.5 – Rewriting Equations and Formulas Example 6 If the campus bookstore needs to have $6600 in revenue from sales of these two items. What are some combinations of T- shirts and sweatshirts that will meet this objective?

1.5 – Rewriting Equations and Formulas HOMEWORK Worksheet 1.5 #1 – 3, 13 – 25 all