You have to be very careful when you use significant figures (sig. figs.). In biology, you want 2 sig figs. In math, maybe 2 or 3 sig figs (depends on the question) If you are even off by a decimal, your answer is wrong. Significant figures are a special type of rounding, rounding where I only take certain decimal places into account (and the rest are garbage). You could do all of this in a calculator and then count how many decimals you want.
