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Significant Figure Calculations

Addition or Subtraction using Significant Figures:
The answer can have no more figures to the right of the decimal point than there are in the measurement with the smallest number of figures to the right of the decimal point.

Example:...2.87 ......(2 sig. figs to the right of the decimal)
........ ..........3.5673 ..(4 sig. figs to the right of the decimal)
...........+ 301.2 .........(1 sig. fig. to the right of the decimal)
..............307.6373--> rounds off to 307.6 (our answer can only have one figure after the decimal)

2. Multiplication or Division using Significant Figures:
The answer can have no more significant figures that there are in the measurement with the smallest number of significant figures.

Example: 12.257.... (5 total significant figures)
.................x 1.162 ....(4 total significant figures)
................14.2426 --> rounds off to 14.24 (4 total significant figures)

HINT: Students often have difficulty remembering the rules for using significant figures in calculations and that makes them very sad…putting them in A SAD MODE.

 A: addition M: multiply S: subtraction O: or A: after D: divide D: decimal E: everything If you Add or Subtract, look After the Decimal for significant figures. If you Multiply Or Divide look at Everything (the entire number) for significant figures.

As a rule, when performing a series of calculations, wait until the very end to round off to the proper number of significant figures instead of rounding off each intermediate result.

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