Question

In how many ways can there be a common tangent between two circles?

(a) 3

(b) 4

(c) 1

(d) 2

This question was posed to me in an interview.

This intriguing question comes from Drawing Tangents and Normals for Different Conditions of Circle topic in section Geometrical Construction of Engineering Drawing

Answer 1

The correct answer is (d) 2

The best explanation: There are two ways in which the circles can have a common tangent. One is internal tangents in which the common tangent is touching the internal part of the circle with respect to the other circle and the other way is external tangent.