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Three Dimensional Geometry · Question 18

JEE Main 2026 (Online) 28th January Morning ShiftMCQMedium📈 Topic in 35% papers+4−1
1

If the distances of the point (1, 2, a) from the line x - 11 = y2 = z - 11 along the lines L1 : x - 13 = y - 24 = z - ab and L2 : x - 11 = y - 24 = z - ac are equal, then a + b + c is equal to

  1. 4
  2. 6
  3. 7
  4. 5

Answer

(3) 7

Solution

Let P(1, 2, a). A point on L1: (1 + 3t, 2 + 4t, a + bt)

It lies on the given line: 3t1 = 2 + 4t2 = a + bt - 11

3t = 1 + 2t t = 1 and a + b - 1 = 3 a + b = 4

meeting point Q1(4, 6, 4), PQ12 = 9 + 16 + b2 = 25 + b2

A point on L2: (1 + s, 2 + 4s, a + cs)

s = 2 + 4s2 = 1 + 2s s = -1 and a - c - 1 = -1 a = c

meeting point Q2(0, -2, 0), PQ22 = 1 + 16 + c2 = 17 + c2

PQ1 = PQ2 c2 - b2 = 8

With c = a = 4 - b: (4 - b)2 - b2 = 8

16 - 8b = 8 b = 1, a = 3, c = 3

a + b + c = 7

Answer: (3)

JEE Main 2026 (Online) 28th January Morning Shift

Keep practising — Three Dimensional Geometry

2

Let Q(a, b, c) be the image of the point P(3, 2, 1) in the line x - 11 = y2 = z - 11. Then the distance of Q from the line x - 93 = y - 92 = z - 5-2 is

  1. 8
  2. 7
  3. 6
  4. 5
JEE Main 2026 (Online) 28th January Evening Shift
3

If the distance of the point P(43, , ), < 0, from the line r = 4 i - k + (2 i + 3 k), R along a line with direction ratios 3, -1, 0 is 13 10, then 2 + 2 is equal to

JEE Main 2026 (Online) 28th January Evening Shift
4

Let the lines L1: r = i + 2 j + 3 k + (2 i + 3 j + 4 k), R and L2: r = (4 i + j) + (5 i + 2 j + k), R, intersect at the point R. Let P and Q be the points lying on lines L1 and L2, respectively, such that | PR| = 29 and | PQ| = 473. If the point P lies in the first octant, then 27(QR)2 is equal to

  1. 360
  2. 348
  3. 320
  4. 340
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5

Let a line L passing through the point P(1, 1, 1) be perpendicular to the lines x-44 = y-11 = z-11 and x-171 = y-711 = z0. Let the line L intersect the yz-plane at the point Q. Another line parallel to L and passing through the point S(1, 0, -1) intersects the yz-plane at the point R. Then the square of the area of the parallelogram PQRS is equal to .

JEE Main 2026 (Online) 24th January Morning Shift
6

The sum of all values of , for which the shortest distance between the lines x+1 = y-2-1 = z-4- and x = y-12 = z-12 is 2, is

  1. -6
  2. -8
  3. 8
  4. 6
JEE Main 2026 (Online) 24th January Evening Shift
7

Let the direction cosines of two lines satisfy the equations : 4l + m - n = 0 and 2mn + 10nl + 3lm = 0. Then the cosine of the acute angle between these lines is :

  1. 107 38
  2. 10 38
  3. 103 38
  4. 203 38
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8

The vertices B and C of a triangle ABC lie on the line x1 = 1 - y-2 = z - 23. The coordinates of A and B are (1, 6, 3) and (4, 9, α) respectively and C is at a distance of 10 units from B. The area (in sq. units) of ABC is :

  1. 20 13
  2. 5 13
  3. 15 13
  4. 10 13
JEE Main 2026 (Online) 23rd January Morning Shift
9

If the image of the point P(a, 2, a) in the line x2 = y + a1 = z1 is Q and the image of Q in the line x - 2b2 = y - a1 = z + 2b-5 is P , then a + b is equal to .

JEE Main 2026 (Online) 23rd January Evening Shift
10

Let P( , , ) be the point on the line x - 12 = y + 1-3 = z at a distance 4 14 from the point (1, -1, 0) and nearer to the origin. Then the shortest distance, between the lines x - 1 = y - 2 = z - 3 and x + 52 = y - 101 = z - 31, is equal to

  1. 4 75
  2. 7 54
  3. 4 57
  4. 2 74
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11

If the image of the point P(1, 2, a) in the line x - 63 = y - 72 = 7 - z2 is Q(5, b, c), then a2 + b2 + c2 is equal to

  1. 298
  2. 264
  3. 293
  4. 283
JEE Main 2026 (Online) 22nd January Morning Shift

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