There are 4 significant figures in this problem.
302.05 grams
There are 4 significant digits
All four of them.
5
3 of them.
302.05 grams
4 of them.
five. 30.002
10.1+25.01+5.08
I would use grams because grams would give you more significant figures for the measurement than kilograms
Three - all nonzero numbers are significant.
Five, since the trailing zero should have been stripped out if it were not significant.