What is negative 78 times negative 64? (-78 x -64)

What is negative 78 times negative 64?

78 times 64 is 4992, but what is the answer if both 78 and 64 are negative numbers? Here we will determine if the answer to negative 78 times negative 64 is positive 4992 or negative 4992.

There are many different ways to explain and determine if the answer to negative 78 times negative 64 is -4992 or +4992 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 -4992 is the correct answer using basic algebra.

We will test if -4992 is correct by setting up the equation negative 78 times negative 64 equals negative 4992, and then simplifying the equation to see if it is true.

(-78) (-64) = (-4992)

Divide both sides of the equation by (-64) :

		(-78) (-64)
		(-64)

		(-4992)
		(-64)

The numerator and denominator on the left side both have (-64) which even each other out and can be removed:

(-78) =

		(-4992)
		(-64)

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

(-78) =

		(4992)
		(64)

A numerator of 4992 and denominator of 64 on the right side is the same as 4992 divided by 64 which is 78. Now we end up with this untrue equation:

(-78) = (78)

-78 is NOT equal to 78, thus we have proven that negative 78 times negative 64 is not equal to -4992. The answer must therefore be 4992:

-78 x -64 = 4992

The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 78 times negative 64 will always have a positive answer.

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