Statistics and Significant Figures

The smaller end of the bolt falls between 57 and 58 millimeters. It is possible to estimate the last digit in this case, which is close to 0.2 millimeters. So, the smaller end of the bolt is on 57.2 millimeters. Since the large end of the bolt is placed exactly on 20.0 millimeters, we can say that the length of the bolt is

57.2 millimeters - 20.0 millimeters = 37.2 millimeters