I have a question regarding significant figures. I understand the notion well, but am having trouble putting it into practice. My main question is: let's say you divide two numbers of 3 sf each. The result from the calculator is long so you round it to 3 sf. If you need to re-use that result in a later calculation, do you (a) use the 3 sf rounded figure, (b) use the number with one additional sf (so 4 sf even though it won't show on paper), or (c) use the exact same number you got from the calculator (containing up to 10 sf, also won't show on paper) ?