What is a significant figure? How do you add, multiply divide or subtract with them?

Question

Hello
I do not understand significant figures AT ALL! Can you please help me?
Are zeros part of them? When can they be part of them? I have a quiz tomorrow and I will have to round significant figures. For example, how does 455.77 round to 456?
When do you round up or down? My teacher is very unclear about this.
Thanks so much
<3

Thank you guys so much I am kind of understanding it now!

Answer 1

go to www.domb.theteterszone.net
and then go to tutorials..and significant figures.
there really easy when u understand them :]
good luck

Answer 2

okay so 455.77 rounds to 456 because if the decimal is 5 or higher and the number before the decimal is odd you round it up, but you leave it alone if it'e even and the decimal is 5 or higher.


okay so here are the rules:

1. All digits 1-9 inclusive are significant figures. Eg. 129 has 3 sig figs

2. Digits between sig figs are always significant. Eg. 5007 has four sig figs

3. trailing zeros in a number are significant ONLY if the number contains a decimal point. Eg. 100.0 has 4 sig figs
100 has 1

4. Zeros in the beginning of a number whose only function is to place the decimal point are not significant. Eg. .00025 has 2 sig figs.

5. Zeros following a decimal sig fig are significant. Eg. 0.000470 has 3 sig figs
0.47000 has 5

okay so in 12.00034 there are 4 sig figs because the zeros are only place holders, but if it's 12.0 there are 3.


0.02 has 1 sig fig
0.020 has 2
501 has 3
201.1 has 4
5000 has 1
5000. has 5 <- if it has a decimal at the end like that it means that the numbers were not counted by tens and that every step it took to get to 5000 was one by one. that's wny some 0s are not significant because is means they were counted by tens. this is showed by either a decimal or a line over one of the numbers
6051.00 has 6
0.0005 has 1
.1020 has 4 <- rule2
10001 has 5

i hope this gets to you in time!!

Answer 3

The rule for addition and subtraction for significant figures is simple: When quantities are added or subtracted, the number of decimal places in the answer is equal to the number of decimal places in the qunatity with the smallest number of decimal places. does that make sense? when multiplying or dividing sig figs, The LEAST number of significant figures in any number of the problem determines the number of significant figures in the answer.

Answer 4

general rules for rounding: Five or more--round UP; Four or less-round down. SIGNIFICANT digits... Example: 7.50...the last zero is NOT significant because 7.5 is the same as 7.50, BUT 7.05 the zero IS significant because 7.05 and 7.5 is NOT the same. Also--0.55 the zero is NOT significant because .55 and 0.55 are the same, but 10.55--the zero IS significant because 10.55 is NOT the same as 1.55

Answer 5

I made a VoiceTHread lecture for my chemistry students that missed the in class lecture that may be of help to you. You can link to it at:

http://voicethread.com/view.php?b=5949