Is 4.05 greater than 4.2

No, 4.05 is not greater than 4.2.

Easier way to look at this is: since both are b, just look at the decimals. For eg, 4.05 becomes 0.05 or 5 and 4.2 becomes 0.2 or 20, and since 20 is bigger than 5, so is 4.2.

No

4.2 is greater than 4.05

basically 4.2 is 4.20 and so 4.05 is smaller