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Three Dimensional Geometry · Question 16

JEE Main 2026 (Online) 2nd April Morning ShiftMCQEasy📈 Topic in 68% papers+4−1
1

Let a line L passing through the point (1, 1, 1) be perpendicular to both the vectors 2 i+2 j+ k and i+2 j+2 k. If P(a, b, c) is the foot of perpendicular from the origin on the line L, then the value of 34(a+b+c) is :

  1. 50
  2. 80
  3. 100
  4. 120

Answer

(3) 100

Solution

Direction of L: (2 i+2 j+ k) ( i+2 j+2 k)= vmatrix i& j& k\\2&2&1\\1&2&2 vmatrix=2 i-3 j+2 k

Any point of L: P(1+2t, 1-3t, 1+2t)

P is the foot from O ⇒ OP L:

2(1+2t)-3(1-3t)+2(1+2t)=0

1+17t=0 t=- 117

a+b+c=(1+2t)+(1-3t)+(1+2t)=3+t= 5017

∴ 34(a+b+c)=100

Answer: (3)

JEE Main 2026 (Online) 2nd April Morning Shift

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2

Let the point A be the foot of perpendicular drawn from the point P(a, b, 0) on the line x-12= y-21= z- 3. If the midpoint of the line segment PA is (0, 34, - 14 ), then the value of a2+b2+ 2 is equal to :

  1. 1
  2. 2
  3. 6
  4. 9
JEE Main 2026 (Online) 2nd April Evening Shift
3

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

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
5

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
6

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
JEE Main 2026 (Online) 24th January Morning Shift
7

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
8

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
9

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

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
11

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

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