if i have a sqaure of length 0.200m, is its volume 0.040 or 0.0400 mcubed?
A square has no volume, only area. Do you mean a cube?
In determining "number of significant figures" there is always an ambiguity as to whether a "0" is "significant" or just a place holder. For that reason, if "significant figures" are important it is best to use "scientific notation". Here "0.200 m" would be best written "2.00 x 10-1 m", showing clearly that there are "3 significant figures".
If you really mean area rather than volume it would be best to write it as 4.00 x 10-2 m2, again showing clearly that there are "3 significant figures".
sorry, i meant the area of a square, ok, so if 2.00 x 10-1 m is its length, would its area be 4.00 x 10-2 m2 or 4.0 x 10-2 m2?
The latter: 4.00 x 10-2 mp2. Since the orginal measurement had 2 three significant figures so must the answer.
It is better, by the way to talk about "significant figures" rather than "decimal places". The number of significant figures in the result of any calculation is the smallest number of significant figures in any number in the calculation. There is no such rule for "decimal places".
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