8 times 40 is 320, but what is the answer if both 8 and 40 are negative numbers? Here we will determine if the answer to negative 8 times negative 40 is positive 320 or negative 320.
There are many different ways to explain and determine if the answer to negative 8 times negative 40 is -320 or +320 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 -320 is the correct answer using basic algebra.
We will test if -320 is correct by setting up the equation negative 8 times negative 40 equals negative 320, and then simplifying the equation to see if it is true.
(-8) (-40) = (-320)
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:
| (-8) = |
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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:
| (-8) = |
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A numerator of 320 and denominator of 40 on the right side is the same as 320 divided by 40 which is 8. Now we end up with this untrue equation:
(-8) = (8)
-8 is NOT equal to 8, thus we have proven that negative 8 times negative 40 is not equal to -320. The answer must therefore be 320:
-8 x -40 = 320
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 8 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 8 times negative 41?
Here is the next problem on our list that we have explained and calculated.
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