Question

Outer diameter is 95 mm and inner diameter is 88 mm. Mean diameter is ________

(a) 90 mm

(b) 91.5 mm

(c) 95.1 mm

(d) 88 mm

I had been asked this question in an interview for job.

The doubt is from Construction of Helical Springs in chapter Curves used in Engineering Practice of Engineering Drawing

Answer 1

The correct choice is (b) 91.5 mm

The explanation is: Mean diameter is average of outer and inner diameter of spring. Difference between the outer and inner diameter gives diameter of wire and ratio of mean diameter to the diameter of wire gives spring index.