## ABSOLUTELY NOT!

- page 1, How to Add, Subtract, Multiply, Divide Signed Numbers - Writtten

 "O.K., How Do You Want It?" If you just wish WRITTEN INSTRUCTIONS on how to compute with signed numbers, use this page. For a "MANIPULATIVE" explanation of why the written instructions are appropriate, use the RESTATE buttons found on the page to link to an animated graphic file. Use your browser to return to this page. PRACTICE is found on other pages linked through the QUESTION buttons. For a CALCULATOR demonstration, press the CALAULATOR button.

 How to Add, Subtract, Multiply, Divide Signed Numbers Though four operations are listed here, there are really only three sets of instructions. This is a reference page with practice give briefly and with more practice given on other pages.

• If the signs are the SAME, use the sign and ADD the absolute values.
• If the signs are DIFFERENT, use the sign of the number larger in absolute value and SUBTRACT the absolute values.
+ 4
+ 3
- 4
- 3
- 4
+ 3
+ 4
- 3

- 4
- 12
2
5
+ 4
- 12
- 7
- 3

How to Subtract Signed Numbers

1st: Change the sign of the second number.
2nd: Use the rules of addition
SUBTRACT:
+ 4
+ 3
- 4
- 3
- 4
+ 3
+ 4
- 3

- 8
- 12
12
-7
+ 6
3
5
- 3

How to Multiply or Divide Signed Numbers

As with the other operations above, the rules are stated, examples and a quiz provided. But, this time take a brief detour for an explanation.

• An ODD number of NEGATIVE SIGNS is NEGATIVE.
• An EVEN number of NEGATIVE SIGNS is POSITIVE.

But Why?

It is convenient to think of multiplication and division of signed numbers in terms of factors and opposites -- more specifically in the kind of computation shown on the Opposites on Your Computer's Calculator page.

The expression (-2)(-4)(3) also means(-1)(2)(-1)(4)(3).

This may be rearranged as (-1)(-1)(2)(4)(3).

But, that's also -(-(12)), the opposite of the opposite of twelve. So, when multiplying or dividing signed numbers, use the number of negative signs to determine the sign of the answer because each opposite of an oppisite is the original number.

MULTIPLY OR DIVIDE:
1. (+ 4)(+ 3) =   2. (- 8) ÷ (- 2) =

3. (- 4)(+ 3) =   4. + 4 ÷ (- 8) =

Quiz. Simplify:
1. (-1)(-1)(-1) =   2. (- 8) ÷ 16 =

3. (4)(3)(-5) =   4. (-8) ÷ (- 8) =

 All Together, Now Now that you've mastered the basics of signed number computation, you are ready to see more than one operation in an expression. Please continue to Lesson 80 on Order of Operations.

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