significant digits?

Question

Tell How many significant figures are in each:

a) .00060030
b) 1.83 X 102
c) 5000

Answer 1

a) 5. The 3 leading zeros are insignificant because they are only there to place the decimal point. The trailing zero is significant because it tells you that the number is known to that level of precision.
b) I'm assuming that this is supposed to be 10^2. If so, there are 3 significant figures.
c) It's unknown. There could be 1, there could be 4. More information is needed (for example, you could write it as 5.00 x 10^3, and then there would be 3).

Answer 2

To the left of the decimal point, all digits are significant, so the answer to c is easy: 4
b) You need to multiply this out to figure it out:
1.83*102 = 186.66000000...
and there are 5 significant digits because trailing zeros do not count
a)only embedded zeros count, so there are 4 between and including the 6 and thet 3