What is negative 9 times negative 42? (-9 x -42)

What is negative 9 times negative 42?

9 times 42 is 378, but what is the answer if both 9 and 42 are negative numbers? Here we will determine if the answer to negative 9 times negative 42 is positive 378 or negative 378.

There are many different ways to explain and determine if the answer to negative 9 times negative 42 is -378 or +378 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 -378 is the correct answer using basic algebra.

We will test if -378 is correct by setting up the equation negative 9 times negative 42 equals negative 378, and then simplifying the equation to see if it is true.

(-9) (-42) = (-378)

Divide both sides of the equation by (-42) :

		(-9) (-42)
		(-42)

		(-378)
		(-42)

The numerator and denominator on the left side both have (-42) which even each other out and can be removed:

(-9) =

		(-378)
		(-42)

The numerator and denominator on the right side both have a minus sign (-) which even each other out and can be removed:

(-9) =

		(378)
		(42)

A numerator of 378 and denominator of 42 on the right side is the same as 378 divided by 42 which is 9. Now we end up with this untrue equation:

(-9) = (9)

-9 is NOT equal to 9, thus we have proven that negative 9 times negative 42 is not equal to -378. The answer must therefore be 378:

-9 x -42 = 378

The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 9 times negative 42 will always have a positive answer.

Negative Times Negative Calculator
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