Chapter 1 - Measurement and Problem Solving - Learning Path Questions and Exercises - Exercises - Page 30: 42

1 mm.

The student has measured as 0.8755m or 875.5 mm. This value has 4 significant figures in which the first 3 figures are directly from the reading on the meter-stick. The last figure has an error in its value. So the reading must have been at the middle of 2 smallest division on the scale i.e. between 875 and 876 mm. So the smallest division of the scale is 1 mm.