Concept
To determine the number of significant figures in a number use the following 3 rules:
1. Non-zero digits are always significant.
2. Any zeros between two significant digits are significant.
3. A final zero or trailing zeros in the decimal portion ONLY are significant.
Let's check through the options:
5,280
This has 3 significant figures
360
This has 2 significant figures
296.54
This has 5 significant figures
18.3
This has 3 significant figures