How many significant figures does 0.0072 contain?

It has 4 significant figures.

Significant Figures

à Non-zero numbers are always significant figures.

à Zeros are tricky:

- If zeros appear before a non-zero (called leading zeros), they are NEVER significant (ex: 0.025)

- If zeros fall between non-zero numbers, they are ALWAYS significant (ex: 205)

- If zeros come at the end of the number, they WILL be significant only IF there is a decimal present (ex: 250.0)

à Exact numbers (or counting numbers) have infinite significant figures. For example, if we count 3 pencils, we know there are exactly 3 pencils. Or, when we say 1 inch = 2.54 cm, we know this is for exactly 1 inch.