Final answer:
When estimating the last digit of a measurement using a ruler, it's important to consider the uncertainty in the measurement. The most reasonable estimate for the length of the blue cylinder is 2.76cm, but 2.72cm or 2.78cm could also be correct. However, 2.755cm would not be a correct measurement because it goes beyond the level of estimation allowed by the ruler.
Step-by-step explanation:
When estimating the last digit in a measurement, it's important to consider the uncertainty in the measurement. In the case of the blue cylinder, the ruler indicates a length between 2.7cm and 2.8cm. Since the ruler does not have markings for hundredths of a centimeter, we can only estimate the last digit. In this case, the most reasonable estimate would be 2.76cm, as it falls between 2.7cm and 2.8cm. However, it's also reasonable to estimate the length as 2.72cm or 2.78cm.
The reason why 2.755cm would not be a correct measurement is that it goes beyond the level of estimation we can make with the ruler. Since the ruler only has markings for tenths of a centimeter, we cannot accurately estimate the hundredths digit. Therefore, it would not be appropriate to include a decimal place that is beyond our level of precision.