So 3 sig figs can be done differently. If you use scientific notation it will be 3.98x10^5
If you just want to round you round the first 3 numbers and add zeroes to the rest of it.
So 398742–> 398700 now since 7 is more than 5 you would round the 8 up to 9.
So 399,000 would be 3 significant figures.
