You wish to measure the distance on a Mercator chart between a point in latitude 42°30'N and a point in latitude 40°30'N. To measure 30 miles at a time you should set the points of the dividers at __________.

Correct Answer: Option D — 41°15' and 41°45'

On a Mercator chart, distance must be measured using the latitude scale at the mid-latitude of the segment being measured. For a track between 40°30'N and 42°30'N, the mid-latitude is 41°30'N. Therefore, the dividers should be centered on 41°30'N, spanning 41°15' to 41°45'.