Answer:
The answer is : uncertainity is 2% and number of significant figures is 3.
Step-by-step explanation:
The original number has an uncertainty of 1%
squaring a number is in other words multiplying it by itself.
in case of multiplication or division of two numbers, their PERCENTAGE uncertainties are added.
(this is not to be confused with addition or subtraction of numbers where ABSOLUTE uncertainties are added.)
so the uncertainty of the square will be:
(20*20) +/- (1+1)%= 400 +/- 2%
Also the number of significant figures in a product is the number of significant figures in the original figures. If the number of significant figures is different : 23.8 * 24.65; then the lesser number is the number of significant figures in the product; i.e. 3 in this case.