Q41 / 90 · JEE Main 2024 (30 Jan Shift 2) · Mathematics

Let A(α,0) and B(0,β) be the points on the line 5x+7y=50. Let the point P divide the line segment AB internally in the ratio 7: 3. Let 3x-25=0 be a directrix of the ellipse E:x2a2+y2b2=1 and the corresponding focus be S. If from S, the perpendicular on the x-axis passes through P, then the length of the latus rectum of E is equal to

  • A
    253
  • B
    329
  • C
    259
  • Correct answer
    D
    325

Solution

Given: A(α,0) and B(0,β) lies on the line 5x+7y=50.

⇒5α+70=50, 50+7β=50

⇒α=10, β=507

Also, P divide the line segment AB internally in the ratio 7: 3.

⇒P≡7×0+3×107+3,7×507+3×07+3

⇒P≡3,5

⇒ae=3 as perpendicular from S passes through P

Now, 3x-25=0 is a directrix of the ellipse E:x2a2+y2b2=1

⇒x=253

We know that, directrix of an ellipse is given by x=±ae

⇒ae=253

Figure

Also, ae=3

⇒a=5, b=4

Length of LR =2b2a=325

Hence, the correct answer is option: 'D'.

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