Science By Numbers

To be accurate is to be right on or very close to the actual number. Precision is how close the numbers are to each other.,http://www.mathsisfun.com/accuracy-precision.html This website gives further information on Accuracy vs Precision.

Significant figures or "sig figs" are  
           1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant.

2) ALL zeroes between non-zero numbers are ALWAYS significant.

3) ALL zeroes which are SIMULTANEOUSLY to the right of the decimal point AND at the end of the number are ALWAYS significant.

4) ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant.

Further information on sig figs can be found at http://www.usca.edu/chemistry/genchem/sigfig.htm where i got the 4 rules listed above.