What is negative 90 times negative 20? (-90 x -20)

What is negative 90 times negative 20?

90 times 20 is 1800, but what is the answer if both 90 and 20 are negative numbers? Here we will determine if the answer to negative 90 times negative 20 is positive 1800 or negative 1800.

There are many different ways to explain and determine if the answer to negative 90 times negative 20 is -1800 or +1800 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 -1800 is the correct answer using basic algebra.

We will test if -1800 is correct by setting up the equation negative 90 times negative 20 equals negative 1800, and then simplifying the equation to see if it is true.

(-90) (-20) = (-1800)

Divide both sides of the equation by (-20) :

		(-90) (-20)
		(-20)

		(-1800)
		(-20)

The numerator and denominator on the left side both have (-20) which even each other out and can be removed:

(-90) =

		(-1800)
		(-20)

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

(-90) =

		(1800)
		(20)

A numerator of 1800 and denominator of 20 on the right side is the same as 1800 divided by 20 which is 90. Now we end up with this untrue equation:

(-90) = (90)

-90 is NOT equal to 90, thus we have proven that negative 90 times negative 20 is not equal to -1800. The answer must therefore be 1800:

-90 x -20 = 1800

The above applies to all math problems where you multiply two negative numbers. Multiplying two negative numbers such as negative 90 times negative 20 will always have a positive answer.

Negative Times Negative Calculator
Here you can multiply another two negative numbers together.

What is negative 90 times negative 21?
Here is the next problem on our list that we have explained and calculated.