Why is it better to use a divider than ruler, while measuring the length of a line segment?

Hint: While using a ruler, if our eyes are not in a perfect vertical position, we may get positioning error.

Both ruler and divider can be used to measure the length of a line segment. While using a ruler, positioning error may occur due to the incorrect positioning of the eye. Divider has points at each end, they can be placed exactly at the ends of the line segment. So, if we use a divider that error is minimized and we can get an accurate result.
$\therefore $ It is better to use a divider than a ruler for accurate length measurement.

Note: The thickness of the ruler may cause difficulties in reading off the length. However the divider gives up accurate measurement. And if our eyes are not vertically on top of the ruler, we may get errors due to angular viewing.