4 times 20 is 80, but what is the answer if both 4 and 20 are negative numbers? Here we will determine if the answer to negative 4 times negative 20 is positive 80 or negative 80.
There are many different ways to explain and determine if the answer to negative 4 times negative 20 is -80 or +80 using mathematical terms such as additive inverse and mathematical laws like the Distribute Law.
We will take a different approach - process of elimination: We will simply test if -80 is the correct answer using basic algebra.
We will test if -80 is correct by setting up the equation negative 4 times negative 20 equals negative 80, and then simplifying the equation to see if it is true.
(-4) (-20) = (-80)
Divide both sides of the equation by (-20) :
|
| = |
|
The numerator and denominator on the left side both have (-20) which even each other out and can be removed:
| (-4) = |
|
The numerator and denominator on the right side both have a minus sign (-) which even each other out and can be removed:
| (-4) = |
|
A numerator of 80 and denominator of 20 on the right side is the same as 80 divided by 20 which is 4. Now we end up with this untrue equation:
(-4) = (4)
-4 is NOT equal to 4, thus we have proven that negative 4 times negative 20 is not equal to -80. The answer must therefore be 80:
-4 x -20 = 80
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 4 times negative 20 will always have a positive answer.
Negative Times Negative Calculator
Here you can multiply another two negative numbers together.
What is negative 4 times negative 21?
Here is the next problem on our list that we have explained and calculated.
Copyright | Privacy Policy | Disclaimer | Contact