Question

What is the representative fraction of the kilometer scale if 20 miles is represented as 5 cm and maximum length to be measured is 5 km? (1 mile = 1.609 km)

(a) 1:4

(b) 1:643600

(c) 1:1.287

(d) 0.7768:1

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

I'm obligated to ask this question of Types of Scales topic in division Scales of Engineering Drawing

Answer 1

Right choice is (b) 1:643600

For explanation: The representative fraction is calculated by the formula, R.F. = length of the drawing ÷ actual length of the object. Here the length of the drawing is 5 cm and the actual length is 20 miles. In R.F. both quantities should be in the same unit. R.F. = 5 ÷ (20 x 1.609 x1000 x 100) = 1:643600.