Multiple Choice
Which of the following measurements contains the correct number of significant figures?
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1. Intro to General Chemistry
Significant Figures
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A student measures the length of a metal bar using a ruler marked in millimeters and records a value of 12.36 cm. Which of the following correctly expresses this measurement with the appropriate number of significant figures?
A
12.36 cm
B
12 cm
C
12.4 cm
D
12.360 cm
Verified step by step guidance1
Understand that significant figures represent the digits in a measurement that are known with certainty plus one estimated digit, reflecting the precision of the measurement tool.
Identify the precision of the ruler used: since it is marked in millimeters, the smallest division is 1 mm, which corresponds to 0.1 cm, allowing measurements to be recorded to two decimal places in centimeters.
Analyze the recorded measurement 12.36 cm: it has four significant figures (1, 2, 3, and 6), indicating the measurement is precise to the hundredths place (0.01 cm).
Compare the given options to the original measurement's precision: 12 cm has only two significant figures, 12.4 cm has three significant figures, 12.360 cm has five significant figures, which is more precise than the ruler allows.
Conclude that the correct expression of the measurement with appropriate significant figures is 12.36 cm, as it matches the precision of the measuring instrument without adding or losing significant digits.
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