84 times 10 is 840, but what is the answer if both 84 and 10 are negative numbers? Here we will determine if the answer to negative 84 times negative 10 is positive 840 or negative 840.
There are many different ways to explain and determine if the answer to negative 84 times negative 10 is -840 or +840 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 -840 is the correct answer using basic algebra.
We will test if -840 is correct by setting up the equation negative 84 times negative 10 equals negative 840, and then simplifying the equation to see if it is true.
(-84) (-10) = (-840)
Divide both sides of the equation by (-10) :
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| = |
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The numerator and denominator on the left side both have (-10) which even each other out and can be removed:
| (-84) = |
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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:
| (-84) = |
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A numerator of 840 and denominator of 10 on the right side is the same as 840 divided by 10 which is 84. Now we end up with this untrue equation:
(-84) = (84)
-84 is NOT equal to 84, thus we have proven that negative 84 times negative 10 is not equal to -840. The answer must therefore be 840:
-84 x -10 = 840
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 84 times negative 10 will always have a positive answer.
Negative Times Negative Calculator
Here you can multiply another two negative numbers together.
What is negative 84 times negative 11?
Here is the next problem on our list that we have explained and calculated.
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