91 times 7 is 637, but what is the answer if both 91 and 7 are negative numbers? Here we will determine if the answer to negative 91 times negative 7 is positive 637 or negative 637.
There are many different ways to explain and determine if the answer to negative 91 times negative 7 is -637 or +637 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 -637 is the correct answer using basic algebra.
We will test if -637 is correct by setting up the equation negative 91 times negative 7 equals negative 637, and then simplifying the equation to see if it is true.
(-91) (-7) = (-637)
Divide both sides of the equation by (-7) :
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| = |
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The numerator and denominator on the left side both have (-7) which even each other out and can be removed:
| (-91) = |
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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:
| (-91) = |
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A numerator of 637 and denominator of 7 on the right side is the same as 637 divided by 7 which is 91. Now we end up with this untrue equation:
(-91) = (91)
-91 is NOT equal to 91, thus we have proven that negative 91 times negative 7 is not equal to -637. The answer must therefore be 637:
-91 x -7 = 637
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 91 times negative 7 will always have a positive answer.
Negative Times Negative Calculator
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