This is a question on curve of intersection of two unequal cylinders. It requires the understanding of the curve of intersection, surface development and seam. Candidate should also note from the drawing that the two cylinders are offset.

The best approach is to draw the plan first, trace the points from the plan and locate the corresponding points on the elevation. The curve of intersection should therefore show a hidden curve due to the offset. Most candidates attempted the question but about 50% solved it correctly, the expected solution is shown in the figure below.