## Describe Situation Using Integers

#### Introduction

When we are given Math word problems to solve, we can use integers to 'translate' the words into Math. For example, if we are given $10 for the day, and spend$3, we can 'translate' the word spend into 'subtract', and create the equation:

10 - 3 = ?

That tells us that we have $7 left.

#### Terms

## Lesson

The golden rule of describing a situation using integers is to think about whether you are increasing or decreasing a value. If you are increasing, then the function should be addition (+); if you are decreasing then the function should be subtraction (-). Another way to think about it is whether a number is 'going up' (addition) or 'going down' (subtraction).

For example, if we are told that a farmer has 15 sheep, and sells 3, we know that the number of sheep he owns is decreasing. Therefore, we are dealing with subtraction. To create the equation, we'd write the following:

Initial value - Amount initial value has decreased by = Remaining value

In this case, that would be:

15 (his starting number of sheep) - 3 (the number of sheep he sold) = 12 (the number of sheep he has left).

Another example: John gets paid $20 to clean his neighbor's car. When he has finished, the neighbor gives him an extra$5 for doing such a good job.

We know that John's final total has increased, so we have to use addition.

So we can use the following:

Initial value + Amount initial value has increased by = Final value

In this case, that would be:

$20 (his original fee) +$5 (his bonus) = ($25 the final amount he was paid.)