Question

A line of length 15 cm at first lied on the profile plane parallel to horizontal plane and then keeping one of its ends fixed turned 30 degrees with respect to horizontal plane and then turned 50 degrees with respect to profile plane. What is the length of the line in top view?

(a) 9.6 cm

(b) 12.99 cm

(c) 7.5 cm

(d) 11.49 cm

This question was addressed to me in a national level competition.

Asked question is from Projection of Line Inclined to both the Planes in section Projection of Lines of Engineering Drawing

Answer 1

Right choice is (b) 12.99 cm

To explain: First imagine the line in profile plane parallel to horizontal plane as here we are asked to find the top view’s length so even if the line is rotated within the horizontal plane the line length will not change and also rotated with respect to the horizontal plane which is calculated as follows 15 x cos (30) = 12.99 cm.