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A confusion related to Significant figures

  1. Apr 6, 2012 #1
    A book says," 0.00052 has two significant figures: 5 and 2"

    Now imagine a scale to measure length and suppose it's least count is 0.00005
    we measure a length and it comes out to be 0.00052 where we are uncertain about the last digit. So if i am understanding the meaning of sig. figures right, shouldn't the no of significant figure be 5 ??
     
  2. jcsd
  3. Apr 6, 2012 #2

    SammyS

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    No.

    You're not at all certain of the 2. You're pretty certain of the 5.

    Leading zeros don't count as sig. fig.s .
     
  4. Apr 6, 2012 #3
    i know the rules..but i am trying to understand how they make sense
    and i've nt got your point :(
     
  5. Apr 6, 2012 #4

    PhanthomJay

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    Supposing you multiply 1734.6 by 0.0001. The answer, which is based on the least number of sig figs in the given values, is 0.2. It is not 0.1735. Why? Well, 0.0001 could actually be say 0.00014, in which case the answer is 0.24284. That's hardly 0.1735. So .0001 has just 1 sig fig, which is why the rule makes sense.
     
  6. Apr 6, 2012 #5
    significant digits are mostly non-zero digits.

    best way to tell how many sig. figs. a number has is to convert it to scientific notation. (DO NOT ROUND OFF)..

    56800 -> 5.68 x 10 ^ 4 5 6 8 three sig figs.

    0.00052 ->5.2 x 10 ^ -4 5 2 two sig figs.

    1000.001 -> 1.000001 x 10 ^ 3 1 0 0 0 0 0 1 seven sig figs.
     
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