eli5 How do decimals and units of area measurement work?

Question

0.9cmx0.9cm = 0.81cm²
9mmx9mm = 81mm²
Do these two numbers equate?

In: 0

Answer 1

I get what you mean
1mm = 0.1cm
hence 9mm = 0.9cm

but 1mm²= 0.01cm²
hence 9mm² = 0.09cm²

your answer is right.
you won’t get 8.1cm² as answer bc square units ≠ length unit