Final answer:
The last digit of a measured number on a non-digital instrument is determined by estimating one digit beyond the smallest precisely known marking, considering the rules of significant figures and rounding accordingly.
Step-by-step explanation:
How to Determine the Last Digit in Any Measured Number on a Non-Digital Instrument
To determine the last digit in any measured number on a non-digital instrument, follow this guidance: Estimate one digit past the smallest precisely known digit or marking. This estimation process accounts for the uncertainty in the measurement and is guided by the concept of significant figures. For example, if a stick appears to be between 36.6 cm and 36.7 cm on a ruler, you estimate the value of the last digit, such as 36.7 cm. The last digit (7 in this case) represents the first uncertain digit, implying that your measurement is accurate to the tenths place but estimated at the hundredths place.
The number of significant figures in any measurement indicates the precision of the measuring tool used. When expressing measured values, never include more digits than your measuring tool can precisely indicate. If a tool measures in centimeters, you cannot report a measurement in hundredths of a centimeter. Likewise, when dealing with whole number measurements, round according to the last significant digit to the left of the decimal point.
The practice of rounding involves deciding how many significant figures to report and adjusting the final digit accordingly. If the digit immediately to the right of the last significant figure is 5 or more, that last figure is increased by 1; if it is less than 5, the last figure remains unchanged.