3.4+Formulas

Section 3.4 - Formulas
A formula is a math equation or expression that includes one or more variables. When you "plug in" numbers for the variables, you get a result. Here's a simple example: When the friendly police officer pulls you over for speeding on the other side of the lake, there's a clever little formula that they use to figure out how much you have to pay: A set fee of $20 and then $10 for each mile over the speed limit. So the formula would be written as 20 + 10m, where "m" represents miles over the speed limit.

If you substitute 5 for m, you get a result of $70. For 10 miles over, you get a result of $120.

Sometimes formulas are equations. The speeding ticket example above could be written as F = 20 + 10m. The "m" is still miles, the "F" is the fine. Above, we tried different numbers of miles over the limit to figure out what the fine would be. However, if the fine were already known and you were just trying to figure out how many miles over it was, the results would be similar. If the fine is $180, how many miles over is that? 180 = 20 + 10m.

In order to use formulas, you must substitute numbers for the variables. In the following equation, some substitutions would make the statement true (both sides would be equal), while others would not: 2A + B = 15. What could A and B be to make this equation true?

Where to from here?
3.1 Variables and Constants 3.2 Terms 3.3 Equations 3.4 Formulas 3.5 Solving for X 3.6 Two Unknown Relative Values Chapter Three Summary Chapter Three Homework