When are zeros significant when found in front of (to the left) of the decimal point?

If a zero is found between important digits, it is important. Zeros are also used as (not salient) holders to the left of digits if the number is in fact a decimal. Example from www.rpi.edu: , a mass of 42 g has two significant digits. Expressed in kilograms, the mass of 0.042kg should still have two significant digits.

Explanation:

Zeros are also used as (not salient) holders to the left of digits if the number is in fact a decimal. Example from www.rpi.edu: "A mass of 42 g has two significant digits. Expressed in kilograms, the mass of 0.042kg should still have two significant digits."

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