55 times 78 is 4290, but what is the answer if both 55 and 78 are negative numbers? Here we will determine if the answer to negative 55 times negative 78 is positive 4290 or negative 4290.
There are many different ways to explain and determine if the answer to negative 55 times negative 78 is -4290 or +4290 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 -4290 is the correct answer using basic algebra.
We will test if -4290 is correct by setting up the equation negative 55 times negative 78 equals negative 4290, and then simplifying the equation to see if it is true.
(-55) (-78) = (-4290)
Divide both sides of the equation by (-78) :
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| = |
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The numerator and denominator on the left side both have (-78) which even each other out and can be removed:
| (-55) = |
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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:
| (-55) = |
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A numerator of 4290 and denominator of 78 on the right side is the same as 4290 divided by 78 which is 55. Now we end up with this untrue equation:
(-55) = (55)
-55 is NOT equal to 55, thus we have proven that negative 55 times negative 78 is not equal to -4290. The answer must therefore be 4290:
-55 x -78 = 4290
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 55 times negative 78 will always have a positive answer.
Negative Times Negative Calculator
Here you can multiply another two negative numbers together.
What is negative 55 times negative 79?
Here is the next problem on our list that we have explained and calculated.
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