Question

You need to measure the diameter of a soda can. Which measuring tool would produce accurate results that you would expect to be the same as those found by others?

Your hand's span

A string cut to the length of the tip of your finger to the bottom of your palm

A meter stick with only centimeters

A ruler with millimeters and centimeters

Answer 1

do you think that "Your hand's span" is the answer?

Answer 2

Well, it's obviously not the first two options, so let's narrow it down to the last two. They both work, so which of the two is more exact? That's what I think I would do.

Answer 3

good job! now between these two answers the meter stick with only centimeters will give you a measurement like 6.2 cm where the digit "2" is an approximation or uncertainty of the measurement, and the ruler with the millimeters will give you a value like 62.5 mm where the last digit "5" will be your approximation or uncertainty.
Now which one to you think will be more accurate?

Anyway, do you know the difference between accuracy and precision? accuracy is how close the measurement is to the real value and depends in how well calibrate is your instrument. If your millimeter ruler is not well calibrate your measurement will not be accurate. I will assume that the two last instruments has been calibrated in a similar way.