Choose the number of significant figures indicated. 0.00666

There are 3 significant figures in the number 0.00666. They are each of the non-zero number 6's. The zero's before a number are not significant. The zeroes AFTER a number ARE significant. 

For example:

0.006660 has four significant figures because there is a zero after nonzeroes. 

0.00666 only has three significant figures because the zeros before a significant figure are not significant.

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