In this lesson, you accomplished two learning goals.
First, you generated an equation or a table of values that can be used to solve a problem that is presented to you in verbal form (a word problem).
A common type of problem you will encounter includes the relationship between distance, rate, and time. The equation:
D = rt
is particularly useful for solving these types of problems.
The relationship between distance, rate, and time is often expressed using a triangle graphic organizer. To solve for one unknown, cover up the variable representing the unknown, and then either multiply or divide the remaining two. If the remaining two unknowns are horizontally arranged, you will multiply. If the remaining two unknowns are vertically arranged, you will divide.
Mouse over each of the letters in the triangle to see these relationships.
Second, you used a table of values to help solve a problem and interpret the solutions.
When working with problems involving money, such as interest rates, sales tax, or discounts, it is helpful to use the relationships to make a table of values to help you solve the problem. For example:
Alana works in a bookstore, and her local sales tax rate is 7.5%. She made a table of purchase subtotals to help her estimate the amount of sales tax that a customer will pay if their purchase is close to a certain amount:
| Amount of Purchase | Amount of Sales Tax |
| $50 | $3.75 |
| $60 | $4.50 |
| $70 | $5.25 |
| $80 | $6.00 |
If a customer purchases $53 worth of books, Alana can use the table to know that the customer will pay close to $3.75 in sales tax. If a customer purchases exactly $70 worth of books, Alana can use the table to know that the customer will pay exactly $5.25 in sales tax.