Transcript MTH 098 - Shelton State Community College

MTH 091
Section 9.5
Formulas and Problem Solving
What Is A Formula?
• A formula is an equation in which variables
are used to describe a relationship.
• We have two objectives for working with
formulas:
1. Solve a formula for one variable, given the
values of the other variables
2. Solve a formula for a specified variable
Solving A Formula When Numbers Are
Given
• Similar to evaluating an expression
• When you substitute the given values into the
equation, one variable will be left over.
• Isolate this variable using the techniques
previously discussed
Examples
1. Using the formula d = rt, find the unknown
variable if d = 195 and t = 3.
1
2. Using the formula A  2 h( B  b) , find the
unknown variable if A = 60, B = 7, and b = 3.
3. The world’s largest sign for Coca-Cola is
located in Arica, Chile. The rectangular sign
has a length of 400 feet and an area of 52400
square feet. Find the width of the sign.
More Examples
4. Using the formula S = 4LW + 2WH, solve for H
if S = 300, L = 10, and W = 5.
5. Using the formula P = a + b + c, solve for b if P
= 37, a = 15, and c = 9.
Solving A Formula When Numbers Are
Not Given
• Isolate the required variable using the same
techniques as when you had numbers.
• If your formula has a fraction, multiply both
sides by the LCD.
Solve each formula for the
specified variable.
x  4y
for y
2 x  5 y  13
for y
1
D  fk
4
for k
More Examples
A  P  PRT
for T
P  abc
for c