assume that you take a measurement with a metric ruler that is divided into individual millimeters. which…

assume that you take a measurement with a metric ruler that is divided into individual millimeters. which measurement has the correct number of significant figures?\na 21 mm\nb 21.0 mm\nc 21.00 mm\nd none of the above
Answer
Explanation:
Step1: Understand significant figures
When using a metric ruler divided into individual millimeters, we can estimate to the tenths - place.
Step2: Analyze option a
21 mm has 2 significant figures. But we can be more precise.
Step3: Analyze option b
21.0 mm has 3 significant figures. The zero is significant as it is a measured digit (estimated to the tenths - place on the ruler).
Step4: Analyze option c
21.00 mm implies a precision that is not achievable with a ruler divided into individual millimeters. We can only estimate to the tenths - place, not the hundredths - place.
Step5: Analyze option d
Since option b is correct, this is incorrect.
Answer:
B. 21.0 mm