How many significant figures are in the measurement of 0.009 millimeters?

In the measurement of 0.009 millimeters, the significant figures are determined by identifying the meaningful digits in the number. Leading zeros, those that precede the first non-zero digit, do not count as significant figures because they are merely placeholders.

Here, the number is presented with two leading zeros before the digit '9'. When evaluating significant figures, we start counting from the first non-zero digit, which in this case is '9'. Thus, there is only one significant figure in this measurement, which is the digit '9' itself. The zeros before '9' do not contribute to the count of significant figures, making the total significant figures one.

This concept of significant figures is crucial in scientific measurements, as it reflects the precision of the measurement being reported.