9 times 40 is 360, but what is the answer if both 9 and 40 are negative numbers? Here we will determine if the answer to negative 9 times negative 40 is positive 360 or negative 360.
There are many different ways to explain and determine if the answer to negative 9 times negative 40 is -360 or +360 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 -360 is the correct answer using basic algebra.
We will test if -360 is correct by setting up the equation negative 9 times negative 40 equals negative 360, and then simplifying the equation to see if it is true.
(-9) (-40) = (-360)
Divide both sides of the equation by (-40) :
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| = |
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The numerator and denominator on the left side both have (-40) which even each other out and can be removed:
| (-9) = |
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The numerator and denominator on the right side both have a minus sign (-) which even each other out and can be removed:
| (-9) = |
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A numerator of 360 and denominator of 40 on the right side is the same as 360 divided by 40 which is 9. Now we end up with this untrue equation:
(-9) = (9)
-9 is NOT equal to 9, thus we have proven that negative 9 times negative 40 is not equal to -360. The answer must therefore be 360:
-9 x -40 = 360
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 9 times negative 40 will always have a positive answer.
Negative Times Negative Calculator
Here you can multiply another two negative numbers together.
What is negative 9 times negative 41?
Here is the next problem on our list that we have explained and calculated.
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