What is negative 78 times negative 42? (-78 x -42)

What is negative 78 times negative 42?

78 times 42 is 3276, but what is the answer if both 78 and 42 are negative numbers? Here we will determine if the answer to negative 78 times negative 42 is positive 3276 or negative 3276.

There are many different ways to explain and determine if the answer to negative 78 times negative 42 is -3276 or +3276 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 -3276 is the correct answer using basic algebra.

We will test if -3276 is correct by setting up the equation negative 78 times negative 42 equals negative 3276, and then simplifying the equation to see if it is true.

(-78) (-42) = (-3276)

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

		(-78) (-42)
		(-42)

		(-3276)
		(-42)

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

(-78) =

		(-3276)
		(-42)

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

(-78) =

		(3276)
		(42)

A numerator of 3276 and denominator of 42 on the right side is the same as 3276 divided by 42 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 42 is not equal to -3276. The answer must therefore be 3276:

-78 x -42 = 3276

The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 78 times negative 42 will always have a positive answer.

Negative Times Negative Calculator
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