Question

A line parallel to profile plane is held at 85 degrees with vertical plane and top view gives 20 cm of length. What is the true length of line?

(a) 1.7 cm

(b) 229 cm

(c) 20.07 cm

(d) 19.9 cm

I have been asked this question by my school principal while I was bunking the class.

This intriguing question comes from True Length of a Straight Line and its Inclinations with the Reference Planes topic in chapter Projection of Lines of Engineering Drawing

Answer 1

Correct answer is (c) 20.07 cm

The best I can explain: True length of line parallel to profile plane and making angle with vertical plane can be of two values either from top view or front view but from side view the length will be given length. As here it is given top view L= 20/cos(5).