Please, check this rounding

((3.14200 * 1.23400) / 12) * ((0.424^2) + (0.424 * 0.951) + (0.951^2)) = 0.480582734

Round the answer to the required level of accuracy, given the fact that each number other than those to be ignored, has been obtained by measurement.

Ignore: power 2, divisor 12

My answers: either 0.4806 which has only 3 sig figs or 0.481
But I am not sure if I could use the latter variant. I'd like to know why in case I can't use 0.481

Thanks.

Your first answer has four sig figs because of the sandwich rule (if surrounded by sig figs, zero becomes significant). The latter is correct.

Strictly speaking your answer cannot be any more precise than 3 digits because the smallest number in your inputs has only 3 digits. This gives you 0.481.

However, despite this limitation, in doing experimental work, scientists often tack on the next digit because it might suggest a little bit more precision.

0.4806 is four sig. figures and implies an accuracy of 0.5 in 4806 i.e. 0.01% so high accuracy !
0.481 implies an accuracy of 0.5 in 481 i.e. 0.1 %
Update: I agree that you should not claim more than 3 sig. figs. because of your input data, so 0.481 is the correct rounded answer to give.