Walking across a heath question

I'm putting this question in the maths forum because it might be a maths vocabulary problem or something, the question says " some students on an expedition to reach the corner of a large rectangular area of Heathland, which is 4 km long and 2 kilometres wide. They need to reach the opposite corner as quickly as possible as they are behind schedule.they estimate that they could walk along the edges of the heath at 5 km per hour and across the heath at 4 kilometres per hour", in which my problem is that when they say across the heath do they mean to walk across it diagonally? 😄

Yes, but it could be any direction you wanted. Diagonally is probably the quickest.