Significant Figures

Here are some numbers with their significant figures (S.F.) given and a reason why:

Number	S.F.	Reason
365	3	All digits from 1 to 9 are significant.
5005	4	Zero digits are significant when between other numbers.
0·0012	2	The zeros show the position of the decimal point. Using standard form, we could write 1·2 × 10-3. This has no leading zeros, but still 2 s.f.
900	3	The zeros here are part of the number.

As we shall see, numbers like 900 are sometimes assumed to have 1 s.f. only!

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