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11th Grade > Mathematics

INTRODUCTION TO THREE DIMENSIONAL GEOMETRY MCQs

Introduction To Three Dimensional Geometry

Total Questions : 49 | Page 2 of 5 pages
Question 11. The point (1,5,-6) lies in which octant?
  1.    Octant II
  2.    Octant IV
  3.    Octant V
  4.    Octant VI
 Discuss Question
Answer: Option C. -> Octant V
:
C
The x and y coordinates are positive and the z coordinate is negative. Hence, it lies in octantV.
Question 12. Which of the following doesn't lie in any octant?
  1.    (1,0,-3)
  2.    (0,0,0)
  3.    (0,-2,-7)
  4.    All of these
 Discuss Question
Answer: Option D. -> All of these
:
D
The points which lie on the coordinateaxes or coordinate planes are not part of any octant.
Question 13. The coordinate planes divide the space into ___ octants.
 Discuss Question

:
The coordinate planes divide the space into eight octants.
Question 14. In which of the following octants is the y-coordinate of a point positive?
  1.    I, II, III, IV
  2.    I, II, V, VI
  3.    III, IV, VII, VIII
  4.    I, II, VII, VIII
 Discuss Question
Answer: Option B. -> I, II, V, VI
:
B
The y-coordinate of a point is positive in the octants I, II, V and VI
Question 15. Three vertices of a parallelogram ABCD are A(3,-1,2), B(1,2,4) and C(-1,1,2). Find the fourth vertex .
  1.    (1,0,2)
  2.    (1,2,0)
  3.    (2,1,0)
  4.    (2,0,1)
 Discuss Question
Answer: Option A. -> (1,0,2)
:
A
Let D(x,y,z) be the fourth vertex of the parallelogram.
The diagonals of a parallelogram bisect each other.
Therefore, the midpoints of AC and BD are the same. Let this be O.
O=(312,1+12,2+22)O=(1,0,2)
Now, O is the midpoint of BD
1+x2=1x=12+y2=0y=24+z2=2z=0
D=(1,0,2)
Question 16. Find the ratio in which the line segment joining the points (4,8,10) and (6,10,-8) is divided by the YZ-plane.
  1.    internally in the ratio 2:3
  2.    externally in the ratio 2:3
  3.    internally in the ratio 1:2
  4.    externally in the ratio 1:2
 Discuss Question
Answer: Option B. -> externally in the ratio 2:3
:
B
Let the YZ-plane divide theline segment joining the points (4,8,10) and (6,10,-8) in the ratio k:1 at the point P.
The x-coordinate of the point P is given by
x=4+6kk+1
Since P lies on the YZ plane, x=0
4+6k=0k=23
Hence, the points are divided by the YZ-plane in the ratio 2:3 externally
Question 17. Find the locus of the point which is at a distance of 3 units from the origin.
  1.    x+y+z=3
  2.    x+y+z=9
  3.    x2+y2+z2=9
  4.    x2+y2+z2=3
 Discuss Question
Answer: Option C. -> x2+y2+z2=9
:
C
Let P(x,y,z) be the required point.
According to the given condition
(x0)2+(y0)2+(z0)2=3x2+y2+z2=9
Question 18. The distance of the point (2,0,-6) from the x-z plane is ___ units.
 Discuss Question

:
The distance of the point P(x,y,z) from the x-z plane is
d=|y|=0units
The point lies on the x-z plane.
Question 19. Which of the following points lie on the x-y plane?
  1.    (1,5,0)
  2.    (0,0,-6)
  3.    (7,0,6)
  4.    (0,2,-5)
 Discuss Question
Answer: Option A. -> (1,5,0)
:
A
For a point on the x-y plane, the z-coordinate is zero and the x and y coordinates are non-zero. Here, (1,5,0) lies on the x-y plane.
Question 20. Which of the following points lie in the VII th octant?
  1.    (1,2,-8)
  2.    (2,-1,-2)
  3.    (-5,0,-4)
  4.    (-2,-3,-10)
 Discuss Question
Answer: Option D. -> (-2,-3,-10)
:
D
In the VII th octant, all three coordinates of a point are negative. Here, only the point (-2,-3,-10) lies in the seventh quadrant.

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