Your measurement should include one estimated digit.
The significant figures in a measurement include all digits measured exactly, plus one estimated digit.
Yes, but then there is no point in using an instrument that is that accurate!
It includes all of the digits that have been measured exactly, plus one estimated digit.
There need no be any estimated digit.
500
There need not be any estimated digit but, if there must be one, then it is the last digit: 3.
Your measurement should include one estimated digit.
The last digit in a measurement indicates the level of precision or uncertainty in the measurement. It is typically an estimate and can vary depending on the instrument's precision or the person taking the measurement. The other digits are considered to be more reliable and accurate in conveying the measurement value.
the estimated digit in 0.503 is 3
A pointless exercise! If it has been measured exactly then what is the point of adding one digit which has been estimated?
The significant figures in a measurement include all digits measured exactly, plus one estimated digit.
Yes, but then there is no point in using an instrument that is that accurate!
the estimated digit in 0.0782m is?
It includes all of the digits that have been measured exactly, plus one estimated digit.
There need no be any estimated digit.
It depends on what kind of measurement you are making, but it would generally be the digit farthest to the right. For example, if you have good eyes and a good ruler, and you are measuring something in millimeters, you can estimate tenths of a millimeter. Suppose the length of a rectangle is between 74 and 75 mm. Look closely between the millimeter marks on the ruler. Suppose the end of the rectangle is about a third of the way from the 74 to the 75, then you good estimate that the length is 74.3 mm. The digit you estimated is the last one, the 3.