Suppose a thermometer has marks at one-degree increments and the meniscus is half-way between the 28 and 29 degrees Celsius marks.

We should properly report the temperature measurement as which of the following?

A) 28°C B) 29°C C) 28.5°C D) 28.50°C E) 28.55°C

C)

Explanation:

If each mark represents one-degree increments than in the half two marks, it represents a half degree. However, we can't affirm that the meniscus (the mark of the liquid in the thermometer) is exactly in the half, so the half-degree in an uncertain number. When we report a number, the uncertain number is the last significant digit of it, thus it must be reported as 28.5°C because at 28.50°C the uncertain would be the 0.