Lesson Objectives
• Demonstrate an understanding of how to translate phrases into algebraic expressions and equations
• Learn the six-step method used for solving applications of linear equations
• Learn how to solve word problems that involve percentages

How to Solve Percent Word Problems

In our last lesson, we reviewed the six-step method used to solve a word problem that involves a linear equation in one variable.

Six-step method for Solving Word Problems with Linear Equations in One Variable

1. Read the problem and determine what you are asked to find
2. Assign a variable to represent the unknown
• If more than one unknown exists, we express the other unknowns in terms of this variable
3. Write out an equation which describes the given situation
4. Solve the equation
5. State the answer using a nice clear sentence
6. Check the result
• We need to make sure the answer is reasonable. In other words, if asked how many students were on a bus, the answer shouldn't be (-4) as we can't have a negative amount of students on a bus.

Solving Percent Word Problems

Another common type of word problem involves percentages. These usually deal with percent increase or percent decrease. Let's look at an example.
Example 1: Solve each word problem
Heather works as a cashier for a local grocery store. After one busy weekend shift, she had a total of $2725 in total receipts. This amount included the 9% state and local sales taxes. What was the amount of the tax collected? Step 1) After reading the problem, it is clear that we need to find the amount of taxes that were collected. Step 2) We have two unknowns, the pre-tax amount of goods and services and the amount of tax collected. let x = amount of pre-tax goods and services sold then .09x = amount of tax collected Step 3) Write an equation, let's think about what we know. If we were to sum the amount of pre-tax goods and services sold (x) with the amount of the tax collected (.09x), we would get 2725 (total receipts): x + .09x = 2725 Step 4) Solve the equation: x + .09x = 2725 We can multiply both sides by 100 and clear the decimal: 100x + 9x = 272,500 109x = 272,500 x = 2500 Step 5) Since x (2500) represents the amount of pre-tax goods and services sold, we have to subtract this away from the total receipts (2725) to get the amount of the tax collected: 2725 - 2500 = 225 We can state our answer as: Heather collected$225 in tax during her shift.
Step 6) We can read back through the problem to check our answer. We want to check that the amount of pre-tax goods and services (2500) plus the amount of the tax collected (225) is equal to the total receipts (2725):
2500 + 225 =  2725
2725 =  2725

Skills Check:

Example #1

Solve each word problem.

This year, Basin City took in $221,100 in tax revenue. This represents a decrease of 40% from the year before. Find the tax revenue for Baskin city for the year before. Please choose the best answer. A$392,000
B
$268,550 C$352,000
D
$368,500 E$292,500

Example #2

Solve each word problem.

Beth is a sales clerk at a local retail store. One day last week, Beth had $2328.48 in receipts for goods sold. This amount included the 8% state and local taxes. Find the pre-tax amount of the goods sold by Beth for the given day. Please choose the best answer. A$1932
B
$1999 C$2156
D
$2130 E$2102

Example #3

Solve each word problem.

At a local nursery, Jessica begs the manager to sell a new palm tree for an all-inclusive price of $10,766. This amount would include the 9% state and local sales taxes, along with the delivery fee of$400.10. If the manager agrees to this price, how much is the price of the palm tree before the tax or delivery fee?

$9920 B$9510
$10,100 D$8917