Exact numbers have an unlimited number of significant figures. For example with numbers like one dozen it is exactly 12.0000000000 with the zeroes repeating forever because numbers such as one dozen are defined as precisely 12 things. Just as one dollar is exactly 100 pennies and so on.
5
5 of them.
Two - the trailing zeros are just placeholders.
52.5765
There are 3 significant figures in 94.2.
4 significant figures.
4 significant figures.
Five significant figures.
4 significant figures.
10 significant figures.
3 of them.
2
two
5 of them.
Three
1
3
4