Report the answer with the proper number of significant figure?

Question

58.17-57.79=0.38 but there are four significant figures here and the answer only contains two? did i do something wrong or do i round the decimals?

for the next couple i did them but can you check if they are right

16.0*0.1879/45.3=0.07 3 significant figures

52.1+18=70.1=70 2 significant figures

76.32*1.53/0.052=0.62 2 significant figures

I'm have problems with that and another question i have is that when is that when you have multiplication and division together like the last problem do you count the bottom portion as apart of the significant figure as well?

Answer 1

ok well...im almost sure i have this right, but not 100%. first, are you supposed to count the significant figures in the whole problem, or solve it then count the sig. figs in the answer?...if its the first then there are 9 significant figures in the whole problem(11 counting the answer)...and if its the second, then there is 2 significant figures in the answer. I don't understand what you mean by "bottom portion".

The significant figures (also called significant digits and abbreviated sig figs) of a number are those digits that carry meaning contributing to its accuracy. Generally this includes all digits except:

leading and trailing zeros where they serve merely as placeholders to indicate the scale of the number

spurious digits introduced, for example, by calculations carried out to greater accuracy than that of the original data, or measurements reported to a greater precision than the equipment supports

Answer 2

1. 0.38 is correct. It only has 2 significant figures.

2. 16 * .1879/45.3 = .06636  = .066

3. 52.1 + 18 = 70.1 = 70

4. 76.32 * 1.53/.052 = 2245.569 = 2200

No. You only count significant figures in the answer. What's in the question doesn't count when it comes to significant figures.