How many significant figures are present in the measurement 0.0009?

• A. 4
• B. 1
• C. 5
• D. 2

Answer: (B)

Verified step by step guidance

1. Identify what significant figures are: Significant figures in a measurement include all the digits that are known with certainty plus one final digit, which is somewhat uncertain or estimated.
2. Look at the given number: 0.0009. Notice that the zeros before the 9 are leading zeros, which serve only to locate the decimal point and are not significant.
3. Determine which digits are significant: In 0.0009, the only non-zero digit is 9, and it is the first significant figure.
4. Conclude the number of significant figures: Since only the digit 9 counts as significant, the measurement 0.0009 has exactly 1 significant figure.
5. Remember that trailing zeros after a decimal point and non-zero digits are significant, but leading zeros are not.