15 times 18 is 270, but what is the answer if both 15 and 18 are negative numbers? Here we will determine if the answer to negative 15 times negative 18 is positive 270 or negative 270.
There are many different ways to explain and determine if the answer to negative 15 times negative 18 is -270 or +270 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 -270 is the correct answer using basic algebra.
We will test if -270 is correct by setting up the equation negative 15 times negative 18 equals negative 270, and then simplifying the equation to see if it is true.
(-15) (-18) = (-270)
Divide both sides of the equation by (-18) :
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| = |
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The numerator and denominator on the left side both have (-18) which even each other out and can be removed:
| (-15) = |
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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:
| (-15) = |
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A numerator of 270 and denominator of 18 on the right side is the same as 270 divided by 18 which is 15. Now we end up with this untrue equation:
(-15) = (15)
-15 is NOT equal to 15, thus we have proven that negative 15 times negative 18 is not equal to -270. The answer must therefore be 270:
-15 x -18 = 270
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 15 times negative 18 will always have a positive answer.
Negative Times Negative Calculator
Here you can multiply another two negative numbers together.
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