21 times 38 is 798, but what is the answer if both 21 and 38 are negative numbers? Here we will determine if the answer to negative 21 times negative 38 is positive 798 or negative 798.
There are many different ways to explain and determine if the answer to negative 21 times negative 38 is -798 or +798 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 -798 is the correct answer using basic algebra.
We will test if -798 is correct by setting up the equation negative 21 times negative 38 equals negative 798, and then simplifying the equation to see if it is true.
(-21) (-38) = (-798)
Divide both sides of the equation by (-38) :
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| = |
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The numerator and denominator on the left side both have (-38) which even each other out and can be removed:
| (-21) = |
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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:
| (-21) = |
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A numerator of 798 and denominator of 38 on the right side is the same as 798 divided by 38 which is 21. Now we end up with this untrue equation:
(-21) = (21)
-21 is NOT equal to 21, thus we have proven that negative 21 times negative 38 is not equal to -798. The answer must therefore be 798:
-21 x -38 = 798
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 21 times negative 38 will always have a positive answer.
Negative Times Negative Calculator
Here you can multiply another two negative numbers together.
What is negative 21 times negative 39?
Here is the next problem on our list that we have explained and calculated.
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