Mathematics · 3D Geometry

JEE Main 2026 — 8 April, Evening Shift — Question 32

Let the foot of perpendicular from the point (λ,2,3) on the line x−41=y−92=z−51\frac{x-4}{1}=\frac{y-9}{2}=\frac{z-5}{1} be the point (1,μ,2).(1,μ,2). Then the distance between the lines x−12=y−23=z+46\frac{x-1}{2}=\frac{y-2}{3}=\frac{z+4}{6} and x−λ2=y−μ3=z+56\frac{x-λ}{2}=\frac{y-μ}{3}=\frac{z+5}{6} is equal to

  1. Option A:

    127\frac{12}{7}

  2. Option B:

    1457\frac{\sqrt{145}}{7}

  3. Option C:

    1467\frac{\sqrt{146}}{7}

    Correct
  4. Option D:

    1437\frac{\sqrt{143}}{7}

Answer: C

Step-by-step solution

x−41=y−92=z−51\frac{x-4}{1}=\frac{y-9}{2}=\frac{z-5}{1}

Q(1,μ,2)\mathrm{Q}(1, \mu, 2) satisfies the line L ∴1−41=μ−92=2−51\therefore \frac{1-4}{1}=\frac{\mu-9}{2}=\frac{2-5}{1} ⇒−3=μ−92=−3⇒μ=3\Rightarrow-3=\frac{\mu-9}{2}=-3 \Rightarrow \mu=3 D.R. of PQ : λ−1,2−μ,1\lambda-1,2-\mu, 1

Since PQ ⊥L⇒(λ−1).1+2(2−μ)+1.1=0\perp \mathrm{L} \Rightarrow(\lambda-1) .1+2(2-\mu)+1.1=0 ⇒λ−2μ+4=0\Rightarrow \lambda-2 \mu+4=0 ∴λ=2\therefore \lambda=2

Now lines : x−12=y−23=z+46\frac{x-1}{2}=\frac{y-2}{3}=\frac{z+4}{6} & x−22=y−33=z+56\frac{x-2}{2}=\frac{y-3}{3}=\frac{z+5}{6} i.e. r⃗=(i^+2j^−4k^)+t1(2i^+3j^+6k^)\vec{r}=(\hat{i}+2 \hat{j}-4 \hat{k})+t_{1}(2 \hat{i}+3 \hat{j}+6 \hat{k}) &r→=(2i^+3j^−5k^)+t2(2i^+3j^+6k^)\& \overrightarrow{\mathrm{r}}=(2 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}-5 \hat{\mathrm{k}})+\mathrm{t}_{2}(2 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}+6 \hat{\mathrm{k}}) Distance =∣((i^+2j^−4k^)−(2i^+3j^−5k^))×(2i^+3j^+6k^)∣∣2i^+3j^+6k^∣=\frac{|((\hat{i}+2 \hat{j}-4 \hat{k})-(2 \hat{i}+3 \hat{j}-5 \hat{k})) \times(2 \hat{i}+3 \hat{j}+6 \hat{k})|}{|2 \hat{i}+3 \hat{j}+6 \hat{k}|} =∣−9i^+8j^−k^∣7=1467=\frac{|-9 \hat{i}+8 \hat{j}-\hat{k}|}{7}=\frac{\sqrt{146}}{7}

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Mathematics
Chapter
3D Geometry
Topic
Skew lines & shortest distance between them