When is zero considered significant

The trailing zero to the right in the decimal place and the zero present between the non zero digit are significant.

Explanation:

The rules which describes about the significant digits are discussed below as:

All the digits which are non zero are significant. Example 178 has three significant digits. The zero which is present in between two non zero digits are consider significant. Example 507 has 3 significant digits. The leading zeroes are not consider significant. Example 0.00676 has 3 significant digits only. Trailing zero to the right in the decimal is consider significant. Example 3.0 has 2 significant digits. Trailing zero which is present in the whole number without any decimal are not significant. Example 9800 has only 2 significant digit.

If a zero is found between significant digits, it is significant. Zeros can be used as (insignificant) place holders to the left of significant digits if the number is a decimal. For example, a mass of 42 g has two significant digits. Expressed in kilograms, the mass of 0.042kg should still have two significant digits.