21 times 35 is 735, but what is the answer if both 21 and 35 are negative numbers? Here we will determine if the answer to negative 21 times negative 35 is positive 735 or negative 735.
There are many different ways to explain and determine if the answer to negative 21 times negative 35 is -735 or +735 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 -735 is the correct answer using basic algebra.
We will test if -735 is correct by setting up the equation negative 21 times negative 35 equals negative 735, and then simplifying the equation to see if it is true.
(-21) (-35) = (-735)
Divide both sides of the equation by (-35) :
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| = |
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The numerator and denominator on the left side both have (-35) 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 735 and denominator of 35 on the right side is the same as 735 divided by 35 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 35 is not equal to -735. The answer must therefore be 735:
-21 x -35 = 735
The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 21 times negative 35 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 36?
Here is the next problem on our list that we have explained and calculated.
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