Q. What do you mean by Rounding off numbers?
Rounding off numbers while you report a calculation your answer should have no more significant figures than the piece of data you used in your computation with the fewest number of significant figures. Therefore if you calculate the density of an object with a mass of 12.33 g in addition to a volume of 19.1 cm3 your answer must have only three significant figures. Though when you divide these quantities using your calculator it will show 0.6455497-lots more figures than you can report in your answer. You must round off the number to three significant figures or 0.646.