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Question 6: What are significant figures? What are the rules for determining significant figures in the final result after addition, subtraction, multiplication and division?

Answer

Significant Figures

In any measurement, the number of accurately known digits and the first doubtful digit are called significant figures.

Rules for finding significant figures

  1. All non-zero digits are significant.
  2. The significance of zero is determined according to the following rules;
    • Zeroes to the left of a sig fig, in simple numbers or decimal fractions, are not significant. For example, 01, 01.2, 0.00651. These numbers have 1, 2 and 3 sig figs, respectively.
    • Zeroes between the sig figs are always significant. Examples 1.205, 10.83.
    • In case of decimal fractions, zeroes to the right of a sig fig are always significant. Examples 5.0, 5.30 have 2 and 3 sig figs, respectively.
    • If the number is an integer, then the significance of zeros to the right depends upon the least count of the measuring instrument.
  3. When the measurement is expressed in scientific notation, all figures before the power of 10 are significant.

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