NDA 2021 Maths · Mathematics · Circles · hard

The number of common tangents to the circles x^2+y^2=1 and (x-5)^2+y^2=4 is

Single correct option

The number of common tangents to the circles

x^2+y^2=1

and

(x-5)^2+y^2=4

Show answer and solution

Answer: (A) $4$

The centres are

5

apart and the radii are

1

and

2

. Since

5>1+2=3

, the circles are separate (neither touching nor overlapping), so they have

2

direct and

2

transverse common tangents,

4

in all.

Original question written in the NDA 2021 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake