5 significant figures.
There are 3 significant figures in '4.50g'
Rounded to two significant figures, 7.42 grams is approximately equal to 7.4 grams.
Three of them.
302.5 grams
302.05 grams
4 of them.
0,000 000 32 has only two significant figures (3 and 2).
32
There are 4 significant figures in this problem.
4
302.05 grams