85 times 99 is 8415, but what is the answer if both 85 and 99 are negative numbers? Here we will determine if the answer to negative 85 times negative 99 is positive 8415 or negative 8415.
There are many different ways to explain and determine if the answer to negative 85 times negative 99 is -8415 or +8415 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 -8415 is the correct answer using basic algebra.
We will test if -8415 is correct by setting up the equation negative 85 times negative 99 equals negative 8415, and then simplifying the equation to see if it is true.
(-85) (-99) = (-8415)
Divide both sides of the equation by (-99) :
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| = |
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The numerator and denominator on the left side both have (-99) which even each other out and can be removed:
| (-85) = |
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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:
| (-85) = |
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A numerator of 8415 and denominator of 99 on the right side is the same as 8415 divided by 99 which is 85. Now we end up with this untrue equation:
(-85) = (85)
-85 is NOT equal to 85, thus we have proven that negative 85 times negative 99 is not equal to -8415. The answer must therefore be 8415:
-85 x -99 = 8415
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 85 times negative 99 will always have a positive answer.
Negative Times Negative Calculator
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