What will be the sign of the product, if we multiply 90 negative integer and 9 positive integer?

To do: Find the sign of the product of $-90$ and $+9$

Solution:

We know that,

positive $\times$ positive = positive integer

negative $\times$ positive  = negative integer

negative $\times$ negative= positive integer

Whenever we multiply negative integers, even number of times, then we get a positive integer.

Since, 90 is even number, multiplication of 90 negative integers is positive integer.

Multiplication of positive integers is always positive, so multiplication of 9 positive integers is positive integer.

Now, if we multiply both, we again get a positive integer.