​Significant Figures

​The number of meaningful digits in a number that convey its meaning according to its accuracy.

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s.f. is short for significant figure(s)

​Rules

1. All non-zero digits are significant (12345)

2. All zeros between non-zero digits are significant​. (109.0043 s.f. = 7)

3. ​Zeros to the right of a decimal point and left of a non-zero digit are NOT significant. (0.0045 s.f. = 2)

4. ​Zeros to the right of the last non-zero digit after a decimal point are significant. (0.003260 s.f. =4)

​Rounding to Given Significant Figures

​To round a number to a given number of significant figures:

• ​Identify the digit in the required significant position.

• ​Note the digit to the immediate right of that position.

• ​If the value of that digit is 5 or greater, round up by adding one to the digit in the required position.

• ​If the value of the digit is less than 5, round down using zeros as place holders.