1. Into how many octants do the coordinate planes divide three-dimensional space?
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Answer: A. 8
Explanation: Three mutually perpendicular coordinate planes divide space into 8 regions called octants.
2. The coordinates of origin in 3D space are:
A. (0, 0, 0)
B. (0, 0)
C. (1, 1, 1)
D. (0, 1, 0)
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Answer: A. (0, 0, 0)
Explanation: The point where all three axes intersect has x=0, y=0, z=0.
3. A point lies on the x-axis. What are its y and z coordinates?
A. y = 0, z = 0
B. x = 0, y = 0
C. x = 0, z = 0
D. x = 1, y = 1
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Answer: A. y = 0, z = 0
Explanation: Any point on the x-axis has coordinates of the form (x, 0, 0).
4. The point (2, -3, 4) lies in which octant?
A. IV octant
B. I octant
C. II octant
D. V octant
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Answer: A. IV octant
Explanation: Signs (+, -, +) correspond to Octant IV (X O Y' Z).
5. Distance of point P(x, y, z) from the origin is given by:
A. √(x² + y² + z²)
B. x + y + z
C. √(x² + y²)
D. x² + y² + z²
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Answer: A. √(x² + y² + z²)
Explanation: Distance from origin O(0,0,0) to P(x,y,z) is √((x-0)² + (y-0)² + (z-0)²).
6. Distance between points P(x₁, y₁, z₁) and Q(x₂, y₂, z₂) is:
A. √((x₂ - x₁)² + (y₂ - y₁)² + (z₂ - z₁)²)
B. (x₂ - x₁) + (y₂ - y₁) + (z₂ - z₁)
C. √((x₂ + x₁)² + (y₂ + y₁)² + (z₂ + z₁)²)
D. √((x₂ - x₁)² + (y₂ - y₁)²)
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Answer: A. √((x₂ - x₁)² + (y₂ - y₁)² + (z₂ - z₁)²)
Explanation: Standard 3D distance formula derived from Pythagorean theorem.
7. Find distance between points (1, 2, 3) and (4, 6, 3):
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Answer: A. 5
Explanation: d = √((4-1)² + (6-2)² + (3-3)²) = √(3² + 4² + 0) = √(9 + 16) = √25 = 5.
8. Midpoint of line joining (x₁, y₁, z₁) and (x₂, y₂, z₂) is:
A. ((x₁+x₂)/2, (y₁+y₂)/2, (z₁+z₂)/2)
B. ((x₁-x₂)/2, (y₁-y₂)/2, (z₁-z₂)/2)
C. (x₁+x₂, y₁+y₂, z₁+z₂)
D. ((x₁+x₂)/3, (y₁+y₂)/3, (z₁+z₂)/3)
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Answer: A. ((x₁+x₂)/2, (y₁+y₂)/2, (z₁+z₂)/2)
Explanation: Standard midpoint formula in 3D geometry.
9. Coordinates of point dividing segment in ratio m : n internally are:
A. ((mx₂ + nx₁)/(m+n), (my₂ + ny₁)/(m+n), (mz₂ + nz₁)/(m+n))
B. ((mx₂ - nx₁)/(m-n), (my₂ - ny₁)/(m-n), (mz₂ - nz₁)/(m-n))
C. ((mx₁ + nx₂)/(m+n), (my₁ + ny₂)/(m+n), (mz₁ + nz₂)/(m+n))
D. ((x₁ + x₂)/m, (y₁ + y₂)/m, (z₁ + z₂)/m)
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Answer: A. ((mx₂ + nx₁)/(m+n), (my₂ + ny₁)/(m+n), (mz₂ + nz₁)/(m+n))
Explanation: Internal section formula for 3D coordinate space.
10. Coordinates of point dividing segment in ratio m : n externally are:
A. ((mx₂ - nx₁)/(m-n), (my₂ - ny₁)/(m-n), (mz₂ - nz₁)/(m-n))
B. ((mx₂ + nx₁)/(m+n), (my₂ + ny₁)/(m+n), (mz₂ + nz₁)/(m+n))
C. ((nx₁ - mx₂)/(m-n), (ny₁ - my₂)/(m-n), (nz₁ - mz₂)/(m-n))
D. ((mx₁ - nx₂)/(m-n), (my₁ - ny₂)/(m-n), (mz₁ - nz₂)/(m-n))
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Answer: A. ((mx₂ - nx₁)/(m-n), (my₂ - ny₁)/(m-n), (mz₂ - nz₁)/(m-n))
Explanation: External section formula substitutes -n for n in internal division formula.
11. Centroid of a triangle with vertices (x₁, y₁, z₁), (x₂, y₂, z₂), and (x₃, y₃, z₃) is:
A. ((x₁+x₂+x₃)/3, (y₁+y₂+y₃)/3, (z₁+z₂+z₃)/3)
B. ((x₁+x₂+x₃)/2, (y₁+y₂+y₃)/2, (z₁+z₂+z₃)/2)
C. (x₁+x₂+x₃, y₁+y₂+y₃, z₁+z₂+z₃)
D. ((x₁+x₂)/3, (y₁+y₂)/3, (z₁+z₂)/3)
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Answer: A. ((x₁+x₂+x₃)/3, (y₁+y₂+y₃)/3, (z₁+z₂+z₃)/3)
Explanation: Centroid is average of x, y, and z coordinates of three vertices.
12. The point (-3, 1, -2) lies in which octant?
A. VI octant
B. III octant
C. VII octant
D. II octant
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Answer: A. VI octant
Explanation: Signs (-, +, -) correspond to Octant VI (X' O Y Z').
13. In xy-plane, the z-coordinate of any point is always:
A. 0
B. 1
C. Any constant
D. Undefined
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Answer: A. 0
Explanation: Equation of xy-plane is z = 0, so all points on it have z = 0.
14. In yz-plane, which coordinate is always zero?
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Answer: A. x
Explanation: Equation of yz-plane is x = 0.
15. Distance of point P(3, 4, 5) from xy-plane is:
A. 5 units
B. 3 units
C. 4 units
D. √(3² + 4²) = 5
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Answer: A. 5 units
Explanation: Distance from xy-plane is given by absolute value of z-coordinate, |5| = 5.
16. Distance of point P(3, 4, 5) from x-axis is:
A. √(y² + z²) = √41
B. 3
C. 4
D. 5
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Answer: A. √(y² + z²) = √41
Explanation: Distance from x-axis to (x, y, z) is √(y² + z²) = √(16 + 25) = √41.
17. Find midpoint of line joining (2, 3, 4) and (4, 7, 8):
A. (3, 5, 6)
B. (6, 10, 12)
C. (1, 2, 2)
D. (2, 4, 4)
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Answer: A. (3, 5, 6)
Explanation: Midpoint = ((2+4)/2, (3+7)/2, (4+8)/2) = (3, 5, 6).
18. The octant in which all three coordinates are negative (-, -, -) is:
A. VII octant
B. VIII octant
C. III octant
D. V octant
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Answer: A. VII octant
Explanation: Octant VII (X' O Y' Z') has negative x, negative y, and negative z.
19. Reflection of point (2, 3, 5) in xy-plane is:
A. (2, 3, -5)
B. (-2, 3, 5)
C. (2, -3, 5)
D. (-2, -3, -5)
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Answer: A. (2, 3, -5)
Explanation: In xy-plane reflection, x and y remain same while sign of z flips.
20. Reflection of point (2, 3, 5) in yz-plane is:
A. (-2, 3, 5)
B. (2, -3, 5)
C. (2, 3, -5)
D. (-2, -3, 5)
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Answer: A. (-2, 3, 5)
Explanation: In yz-plane reflection, y and z remain same while sign of x flips.
21. Foot of perpendicular from point (2, 3, 4) on x-axis is:
A. (2, 0, 0)
B. (0, 3, 0)
C. (0, 0, 4)
D. (2, 3, 0)
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Answer: A. (2, 0, 0)
Explanation: On x-axis, y and z coordinates become 0 while x remains identical.
22. Foot of perpendicular from point (2, 3, 4) on xy-plane is:
A. (2, 3, 0)
B. (2, 0, 4)
C. (0, 3, 4)
D. (2, 0, 0)
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Answer: A. (2, 3, 0)
Explanation: On xy-plane, z-coordinate is 0 while x and y remain identical.
23. If points (1, 1, 1), (0, 0, 0) and (x, y, z) are collinear, then:
A. x = y = z
B. x + y + z = 0
C. x + y = z
D. x = y = -z
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Answer: A. x = y = z
Explanation: Line joining origin (0,0,0) and (1,1,1) has direction ratios 1:1:1, so any point on it has x = y = z.
24. Distance between points (0, 0, 0) and (-3, 4, 12) is:
A. 13
B. 12
C. 5
D. √169 = 13
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Answer: A. 13
Explanation: d = √((-3)² + 4² + 12²) = √(9 + 16 + 144) = √169 = 13.
25. Centroid of triangle with vertices (1, 2, 3), (3, 0, 1), and (-1, 4, 2) is:
A. (1, 2, 2)
B. (3, 6, 6)
C. (1, 3, 2)
D. (2, 2, 2)
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Answer: A. (1, 2, 2)
Explanation: Centroid = ((1+3-1)/3, (2+0+4)/3, (3+1+2)/3) = (3/3, 6/3, 6/3) = (1, 2, 2).
26. What is the equation of xz-plane?
A. y = 0
B. x = 0
C. z = 0
D. x + z = 0
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Answer: A. y = 0
Explanation: In xz-plane, y-coordinate of every point is equal to 0.
27. Ratio in which yz-plane divides segment joining (2, 4, 5) and (3, 5, -4) is:
A. -2 : 3 (externally)
B. 2 : 3 (internally)
C. 3 : 2 (internally)
D. 1 : 2
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Answer: A. -2 : 3 (externally)
Explanation: Ratio = -x₁ : x₂ = -2 : 3. Negative sign indicates external division in 2 : 3.
28. Length of diagonal of a cuboid with sides a, b, c is:
A. √(a² + b² + c²)
B. a + b + c
C. √(a² + b²)
D. 2(ab + bc + ca)
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Answer: A. √(a² + b² + c²)
Explanation: Space diagonal of cuboid with vertices from (0,0,0) to (a,b,c) is √(a² + b² + c²).
29. Coordinates of point on z-axis at distance 5 from origin are:
A. (0, 0, ±5)
B. (±5, 0, 0)
C. (0, ±5, 0)
D. (5, 5, 5)
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Answer: A. (0, 0, ±5)
Explanation: Points on z-axis have x=0, y=0. Distance 5 means z = ±5.
30. Signs of coordinates in Octant VIII (X O Y' Z') are:
A. (+, -, -)
B. (-, -, -)
C. (+, +, -)
D. (-, +, -)
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Answer: A. (+, -, -)
Explanation: Octant VIII corresponds to positive x, negative y, and negative z: (+, -, -).