Question

A line AB of length 20 cm is placed in 1st quadrant and parallel to profile plane and the end A and B are 15, 10 cm away from the horizontal plane respectively. The length of the line in the top view is ______ cm.

(a) 11.18

(b) 13.2

(c) 17.32

(d) 19.36

This question was posed to me by my college professor while I was bunking the class.

This intriguing question originated from Projection of Straight Lines Parallel to Plane in chapter Projection of Lines of Engineering Drawing

Answer 1

Right answer is (d) 19.36

To elaborate: The distance between the projectors drawn from A and B to horizontal plane gives the length of line in top view given the line parallel to profile plane. The difference in distances from A and B to horizontal plane is 5 (15-10). Given length is 20 cm so required length is √(〖20〗^2-5^2 )= 19.36 cm.