2 times 9 is 18, but what is the answer if both 2 and 9 are negative numbers? Here we will determine if the answer to negative 2 times negative 9 is positive 18 or negative 18.
There are many different ways to explain and determine if the answer to negative 2 times negative 9 is -18 or +18 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 -18 is the correct answer using basic algebra.
We will test if -18 is correct by setting up the equation negative 2 times negative 9 equals negative 18, and then simplifying the equation to see if it is true.
(-2) (-9) = (-18)
Divide both sides of the equation by (-9) :
|
| = |
|
The numerator and denominator on the left side both have (-9) which even each other out and can be removed:
| (-2) = |
|
The numerator and denominator on the right side both have a minus sign (-) which even each other out and can be removed:
| (-2) = |
|
A numerator of 18 and denominator of 9 on the right side is the same as 18 divided by 9 which is 2. Now we end up with this untrue equation:
(-2) = (2)
-2 is NOT equal to 2, thus we have proven that negative 2 times negative 9 is not equal to -18. The answer must therefore be 18:
-2 x -9 = 18
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 2 times negative 9 will always have a positive answer.
Negative Times Negative Calculator
Here you can multiply another two negative numbers together.
What is negative 2 times negative 10?
Here is the next problem on our list that we have explained and calculated.
Copyright | Privacy Policy | Disclaimer | Contact