A confusion related to Significant figures

1. Apr 6, 2012

babita

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. Apr 6, 2012

SammyS

Staff Emeritus
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 .

3. Apr 6, 2012

babita

i know the rules..but i am trying to understand how they make sense
and i've nt got your point :(

4. Apr 6, 2012

PhanthomJay

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.

5. Apr 6, 2012

Genoseeker

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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