Which is greater. 021 or. 04?

0.4 because think of it as 0.2 and 0.4. 0.4 would be greater than 0.2

Well think of it this way

which is bigger 21 or 40?

40 correct

this rule applies to decimals as well, as long as they are not a negative integer

this number is not negative, and therefore, the number that looks bigger actually is bigger

and we know that 4 is bigger than 2, and since there both are written in the hundredth place of the decimal, we can safely conclude that 0.04 is bigger than 0.021