Addition and Subtraction:

Addition and Subtraction with Positive and Negative Numbers

The key to knowing whether to add or subtract is to know what kind of numbers you are working with; positive or negative numbers. It is up to us to determine what we’re working with, and practicing multiple types of problems is important in becoming familiar with the different kinds of numbers. This video will review what we have covered on addition and subtraction with positive and negative numbers:

Video Source (08:49 mins) | Transcript

Additional Resources

Khan Academy: Adding & Subtracting Negative Numbers (04:06 mins, Transcript)

Practice Problems

Evaluate the following expression:

\(4-9=?\)
\(7+(-9)=?\)
\(10-(-7)=?\)
\(-8+4=?\)
\(-4+(-4)=?\)
\(-8-(-4)=?\)

Solutions

\(-5\) (Written Solution)

Subtraction can be rewritten as the addition of the opposite. We can change this problem to addition by turning \(-9\) into \(+(-9)\).

\(4-9=-5\) is the same as \(4+( - 9)=-5\)
\(-2\) (Solution Video | Transcript)
17 (Written Solution)

Subtraction can be rewritten as the addition of a negative number.

To solve this problem, we can turn the subtraction to addition by adding the opposite of \(-7\) which is 7.

Our problem \(10-( -7 )\) becomes: \(10+( 7 )=17\)
\(-4\) (Solution Video | Transcript)
\(-8\)
\(-4\)