Mathematics · Ellipse

JEE Main 2026 — 24 January, Morning Shift — Question 7

  1. Let each of the two ellipses E1:x2a2+y2 b2=1,(a>b)\mathrm{E}_{1}: \frac{\mathrm{x}^{2}}{\mathrm{a}^{2}}+\frac{\mathrm{y}^{2}}{\mathrm{~b}^{2}}=1,(\mathrm{a}>\mathrm{b}) and E2:x2 A2+y2 B2=1,( A<B)\mathrm{E}_{2}: \frac{\mathrm{x}^{2}}{\mathrm{~A}^{2}}+\frac{\mathrm{y}^{2}}{\mathrm{~B}^{2}}=1,(\mathrm{~A}<\mathrm{B}) have eccentricity 45\frac{4}{5}. Let the lengths of the latus recta of E1\mathrm{E}_{1} and E2\mathrm{E}_{2} be ℓ1\ell_{1} and ℓ2\ell_{2}, respectively, such that 2ℓ12=9ℓ22 \ell_{1}^{2}=9 \ell_{2}. If the distance between the foci of E1\mathrm{E}_{1} is 8 , then the distance between the foci of E2\mathrm{E}_{2} is
  1. Option A:

    965\frac{96}{5}

  2. Option B:

    325\frac{32}{5}

    Correct
  3. Option C:

    165\frac{16}{5}

  4. Option D:

    85\frac{8}{5}

Answer: B

Step-by-step solution

2ae=8⇒a=52 \mathrm{ae}=8 \Rightarrow \mathrm{a}=5

b2=a2(1−e2)\mathrm{b}^{2}=\mathrm{a}^{2}\left(1-\mathrm{e}^{2}\right)

b2=a2×925 b2=9\mathrm{b}^{2}=\mathrm{a}^{2} \times \frac{9}{25} \quad \mathrm{~b}^{2}=9

E1:x225+y29=1\mathrm{E}_{1}: \frac{\mathrm{x}^{2}}{25}+\frac{\mathrm{y}^{2}}{9}=1

ℓ1:2 b2a=2×95=185\ell_{1}: \frac{2 \mathrm{~b}^{2}}{\mathrm{a}}=\frac{2 \times 9}{5}=\frac{18}{5}

A2=B2(1−e2)⇒A2=925 B2⇒ A=35 B\mathrm{A}^{2}=\mathrm{B}^{2}\left(1-\mathrm{e}^{2}\right) \Rightarrow \mathrm{A}^{2}=\frac{9}{25} \mathrm{~B}^{2} \Rightarrow \mathrm{~A}=\frac{3}{5} \mathrm{~B}

2ℓ2=9ℓ2⇒2(185)2=9ℓ2⇒ℓ2=4×18252 \ell^{2}=9 \ell_{2} \Rightarrow 2\left(\frac{18}{5}\right)^{2}=9 \ell_{2} \Rightarrow \ell_{2}=\frac{4 \times 18}{25}

2 A2 B=7225⇒ A2=3625 B\frac{2 \mathrm{~A}^{2}}{\mathrm{~B}}=\frac{72}{25} \Rightarrow \mathrm{~A}^{2}= \frac{36}{25} \mathrm{~B}

925 B2=36 B25⇒ B=4\frac{9}{25} \mathrm{~B}^{2}=\frac{36 \mathrm{~B}}{25} \Rightarrow \mathrm{~B}=4,

Distance between focii 2Be=2×45×4=3252 \mathrm{Be}=2 \times \frac{4}{5} \times 4=\frac{32}{5}

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Mathematics
Chapter
Ellipse
Topic
position of a Line or point wrt an Ellipse
7. Let each of the two ellipses E 1 : frac x 2 a 2 +frac y 2 b 2 =1,(… | JEE Main 2026 PYQ with Solution · DhiX AI