77 times 15 is 1155, but what is the answer if both 77 and 15 are negative numbers? Here we will determine if the answer to negative 77 times negative 15 is positive 1155 or negative 1155.
There are many different ways to explain and determine if the answer to negative 77 times negative 15 is -1155 or +1155 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 -1155 is the correct answer using basic algebra.
We will test if -1155 is correct by setting up the equation negative 77 times negative 15 equals negative 1155, and then simplifying the equation to see if it is true.
(-77) (-15) = (-1155)
Divide both sides of the equation by (-15) :
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| = |
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The numerator and denominator on the left side both have (-15) which even each other out and can be removed:
| (-77) = |
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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:
| (-77) = |
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A numerator of 1155 and denominator of 15 on the right side is the same as 1155 divided by 15 which is 77. Now we end up with this untrue equation:
(-77) = (77)
-77 is NOT equal to 77, thus we have proven that negative 77 times negative 15 is not equal to -1155. The answer must therefore be 1155:
-77 x -15 = 1155
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 77 times negative 15 will always have a positive answer.
Negative Times Negative Calculator
Here you can multiply another two negative numbers together.
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