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NCERT Solutions for class 12 Maths | Chapter 11 - Three Dimensional Geometry

(1) The area of the quadrilateral ABCD, where A(0, 4, 1), B(2, 3, -1), C(4, 5, 0) and D(2, 6, 2) is equal to
[A] 9 sq. units
[B] 18 sq. units
[C] 27 sq. units
[D] 81 sq. units
Answer: 9 sq. units
(2) The reflection of the point (a, β, γ) in the xy-plane is
[A] (α, β, 0)
[B] (0, 0, γ)
[C] (- α, – β, γ)
[D] (α, β, γ)
Answer: (α, β, γ)

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(3) The equation of the plane through point (1, 2, -3) which is parallel to the plane 3x- 5y + 2z = 11 is given by
[A] 3x – 5y + 2z – 13 = 0
[B] 5x – 3y + 2z + 13 = 0
[C] 3x – 2y + 5z + 13 = 0
[D] 3x – 5y + 2z + 13 = 0
Answer: 3x – 5y + 2z + 13 = 0
(4) The line x = 1, y = 2 is
[A] parallel to x-axis
[B] parallel to y-axis
[C] parallel to z-axis
[D] None of these
Answer: parallel to z-axis
(5) If a line makes angles α, β, γ with the axis then cos 2α + cos 2β + cos 2γ =
[A] -2
[B] -1
[C] 1
[D] 2
Answer: -1
(6) If α, β, γ are the angle which a half ray makes with the positive directions of the axis then sin²α + sin²β + sin²γ =
[A] 1
[B] 2
[C] 0
[D] -1
Answer: 2
(7) The plane x + y = 0
[A] is parallel to z-axis
[B] is perpendicular to z-axis
[C] passes through z-axis
[D] None of these
Answer: passes through z-axis
(8) The locus of xy + yz = 0 is
[A] A pair of st. lines
[B] A pair of parallel lines
[C] A pair of parallel planes
[D] A pair of perpendicular planes
Answer: A pair of perpendicular planes
(9) The equation of the plane through the origin and parallel to the plane 3x – 4y + 5z + 6 = 0
[A] 3x – 4y – 5z – 6 = 0
[B] 3x – 4y + 5z + 6 = 0
[C] 3x – 4y + 5z = 0
[D] 3x + 4y – 5z + 6 = 0
Answer: 3x – 4y + 5z = 0
(10) The direction ratios of the line of intersection of the planes 3x + 2y – z = 5 and x – y + 2z = 3 are
[A] 3, 2, -1
[B] -3, 7, 5
[C] 1, -1, 2
[D] – 11, 4, -5
Answer: -3, 7, 5
(11) The direction ratios of the normal to the plane 7x + 4y – 2z + 5 = 0 are
[A] 7, 4,-2
[B] 7, 4, 5
[C] 7, 4, 2
[D] 4, -2, 5
Answer: 7, 4,-2
(12) If a line makes angles Q1, Q21 and Q3 respectively with the coordinate axis then the value of cos² Q1 + cos² Q2 + cos² Q3
[A] 2
[B] 1
[C] 4
[D] 3/2
Answer: 1
(13) The distance of the point (-3, 4, 5) from the origin
[A] 50
[B] 5√2
[C] 6
[D] None of these
Answer: 5√2
(14) The equation x² – x – 2 = 0 in three dimensional space is represented by
[A] A pair of parallel planes
[B] A pair of straight lines
[C] A pair of perpendicular plane
[D] None of these
Answer: A pair of parallel planes
(15) How many lines through the origin in make equal angles with the coordinate axis?
[A] 1
[B] 4
[C] 8
[D] 2
Answer: 8
(16) The direction cosines of any normal to the xy plane are
[A] 1, 0 ,0
[B] 0, 1, 0
[C] 1, 1, 0
[D] 1, 1, 0
Answer: 1, 1, 0
(17) The equation xy = 0 in three dimensional space is represented by
[A] a plane
[B] two plane are right angles
[C] a pair of parallel planes
[D] a pair of st. line
Answer: two plane are right angles
(18) (2, – 3, – 1) 2x – 3y + 6z + 7 = 0
[A] 4
[B] 3
[C] 2
[D] 1/5
Answer: 3
(19) If 2x + 5y – 6z + 3 = 0 be the equation of the plane, then the equation of any plane parallel to the given plane is
[A] 3x + 5y – 6z + 3 = 0
[B] 2x – 5y – 6z + 3 = 0
[C] 2x + 5y – 6z + k = 0
[D] None of these
Answer: 2x + 5y – 6z + k = 0
(20) The distance of the plane 2x – 3y + 6z + 7 = 0 from the point (2, -3, -1) is
[A] 4
[B] 3
[C] 2
[D] 1/5
Answer: 2

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