Round off to 3 significant figures:
(i)`20.96`
(ii)`0.0003125`

Explanation

(i)`20.96` has four significant figures. The fourth significant figure is more than 5 and hence on rounding off to three significant figures, the given measurement will become `20.9+0.1"i.e.,"21.0.`
(ii)`0.0003125` has four significant figures. The fourth isgnificant figure is 5 and hence on rounding off to three significant figures, the given measurement will become `0.000312 "or" 3.12xx10^(-4)`. This is because 2 before 5 is an even number.