the order of these numbers from largest to smallest are:
3.50, 3.05, 3.005
the way to work them out is by comparing one digit at a time with the rest.
they all start with 3 units therefore that does not help.
then the 1st digit after the decimal point needs comparing: 5 is the biggest therefore 3.50 is the largest of the three numbers.
the 2nd number after the decimal point needs comparing to work out the next largest number: they are both 0 so need to move on to next digit.
the 3rd number after the decimal needs comparing: 5 is the biggest of the two numbers therefore 3.05 is the next largest.