What is the Rule about significant figures when adding or subtracting measurements?

Answer 1

For multiplication and division, you keep the number of significant figures (sig figs) that were in the number with the lesser number of figures. For example, 12345 divided by 555 on a calculator gives 22.243243... but you would represent this as 22.2 because 555 has only 3 sig figs. That said, sig figs are a bit silly in that 99 is much more significant than 10, though both have two digits. Going from 99 to 100 is a 1% change, but going from 10 to 11 is a 10% change. When doing calculations, you should in general NOT round intermediate answers to sig figs, but only the final answer. It's usually best if possible to do the calculation symbolically (such as X is the number instead of 12345) and solve for your final answer, and THEN do all the calculations at once on a calculator, rather than writing down lots of intermediate values (and rounding many out of laziness.) Alternatively, do the calculations in a spreadsheet where you can show all intermediate numbers but preserve them to their full significance, and be able to check your work, unlike with most calculators.

Answer 2

The rule for significant figures is that when adding, subtracting, dividing, or applying any mathematical treatment, one cannot calculate a result that has more significant digits than that of the input with the least number of significant digits. This is because any result cannot be more accurate than the least accurate input.

Answer 3

The least number of significant figures in any number of the problem determines the number of significant figures in the answer.

Answer 4

you take the lowest significant figure in the equation and that is the sig fig of your answer