90 times 90

90 * 90 = 8100

It's 1800.

This is an easier way.

To find the answer, multiply 9 by 9.

$$9*9=\boxed{81}$$

Now add the two zeros to 81 and you got your answer...

$$81\Rightarrow\boxed{8,100}$$

So,  $$8,100$$  Is the answer.