JEE Main 2021 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 17 March 2021, Shift 1, Maths Q74

Question 74 of 90 in this shift, Maths question 14 of 30, Section A.

The line

2x-y+1=0

is a tangent to the circle at the point

(2, 5)

and the centre of the circle lies on

x-2y=4

. Then, the radius of the circle is :

(1) $5\sqrt{3}$
(2) $5\sqrt{4}$
(3) $4\sqrt{5}$
(4) $3\sqrt{5}$ Official answer

Official answer

Option 4

NTA final key.

Chapter: Conic Sections
Topic: Circle Tangents
Idea tested: Normal Passes Through Center

Same idea in other shifts

Asked 4× in all

13 Apr 2023, Shift 2 · Q13Let the centre of a circle C be $(\alpha,\beta)$ and its radius $r<8$ . Let $3x+4y=24$ and $3x-4y=32$ be two tangents and $4x+3y=1$ be a…MediumSingle correct
28 Jun 2022, Shift 1 · Q30Let the lines $y+2x=\sqrt{11}+7\sqrt{7}$ and $2y+x=2\sqrt{11}+6\sqrt{7}$ be normal to a circle $C:(x-h)^2+(y-k)^2=r^2$ . If the line…HardNumerical value
25 Feb 2021, Shift 1 · Q62Let the lines $(2-i)z = (2+i)\bar{z}$ and $(2+i)z + (i-2)\bar{z} - 4i = 0$ , (here $i^2 = -1$ ) be normal to a circle C. If the line…HardSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.