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Saturday, 10 October

JEE Main 2025 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 7 April 2025, Shift 2, Maths Q8

Question 8 of 75 in this shift, Maths question 8 of 25, Section A.

Let pp be the number of all triangles that can be formed by joining the vertices of a regular polygon PP of nn sides and qq be the number of all quadrilaterals that can be formed by joining the vertices of PP. If p+q=126p+q=126, then the eccentricity of the ellipse x216+y2n=1\frac{x^2}{16}+\frac{y^2}{n}=1 is :
  1. (1)12\frac{1}{2}
  2. (2)12\frac{1}{\sqrt{2}}Official answer
  3. (3)74\frac{\sqrt{7}}{4}
  4. (4)34\frac{3}{4}

Official answer

Option 2

NTA final key.

Chapter
Permutations and Combinations
Topic
Permutations and Combinations
Idea tested
Number of Triangles from Points

Same idea in other shifts

Asked 3× in all
  1. 2 Apr 2026, Shift 2 · Q7Let pnp_n denote the total number of triangles formed by joining the vertices of an nn-side regular polygon. If pn+1−pn=66p_{n+1} - p_n = 66,…EasySingle correct
  2. 16 Mar 2021, Shift 2 · Q73Consider a rectangle ABCD having 5, 7, 6, 9 points in the interior of the line segments AB, CD, BC, DA respectively. Let α\alpha be the…MediumSingle 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 42 of the 174 JEE Main shifts held from 2017 to 2026.