Which of the following measurements contains the correct number of significant figures?

• A. 1.0300 has three significant figures.
• B. 120.0 has two significant figures.
• C. 500 has three significant figures.
• D. 0.00450 has three significant figures.

Answer: (D)

Verified step by step guidance

1. Review the rules for counting significant figures: all nonzero digits are significant; zeros between nonzero digits are significant; leading zeros are not significant; trailing zeros in a decimal number are significant.
2. Analyze the first measurement, 1.0300: it has digits 1, 0, 3, 0, 0. The zeros after the decimal and after the 3 are trailing zeros in a decimal number, so they are significant, giving 5 significant figures, not 3.
3. Analyze the second measurement, 120.0: the digits are 1, 2, 0, and a trailing zero after the decimal point. Trailing zeros after a decimal point are significant, so this number has 4 significant figures, not 2.
4. Analyze the third measurement, 500: without a decimal point, trailing zeros are not significant, so this number has 1 significant figure, not 3.
5. Analyze the fourth measurement, 0.00450: leading zeros are not significant, but the digits 4, 5, and the trailing zero after 5 (since it is after the decimal point) are significant, so this number has exactly 3 significant figures.