68 practice questions on Three Dimensional Geometry , sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Three Dimensional Geometry notes .
z x y O P (x, y, z) Three mutually perpendicular axes x, y, z meeting at the origin O, with a point P located by its (x, y, z) coordinates.
Easy - 20 questions Q1.
Direction cosines of a line are the cosines of angles made with the:
A xy, yz and xz planesB x, y and z axesC x-axis onlyD OriginShow answer & explanation →
Q2.
For direction cosines l, m, n of a line:
A l + m + n = 1B lmn = 1C l<sup>2</sup> + m<sup>2</sup> + n<sup>2</sup> = 1D l<sup>2</sup> + m<sup>2</sup> + n<sup>2</sup> = 0Show answer & explanation →
Q3.
The direction ratios of a line are proportional to its:
A Coordinates onlyB InterceptsC SlopesD Direction cosinesShow answer & explanation →
Q5.
The distance from the origin to point P(a, b, c) is:
A a + b + cB sqrt(a + b + c)C a<sup>2</sup> + b<sup>2</sup> + c<sup>2</sup>D sqrt(a<sup>2</sup> + b<sup>2</sup> + c<sup>2</sup>)Show answer & explanation →
Q6.
The vector equation of a line through point A (position vector a) with direction vector b is:
A r = b + lambda*aB r = a + lambda*bC r = lambda*(a + b)D r = a*bShow answer & explanation →
Q7.
The Cartesian equation of a line through (x<sub>1</sub>,y<sub>1</sub>,z<sub>1</sub>) with direction ratios a,b,c is:
A x/a = y/b = z/c, without referencing the given pointB ax + by + cz = 0, the plane equation formC x + y + z = constant, a single linear relationD (x-x<sub>1</sub>)/a = (y-y<sub>1</sub>)/b = (z-z<sub>1</sub>)/cShow answer & explanation →
Q8.
The general equation of a plane is of the form:
A ax + by + cz + d = 0B ax + by = 0C ax<sup>2</sup> + by<sup>2</sup> + cz<sup>2</sup> = 0D x/a = y/b = z/cShow answer & explanation →
Q9.
Two lines in 3D that do not intersect and are not parallel are called:
A Coincident linesB Perpendicular linesC Coplanar linesD Skew linesShow answer & explanation →
Q11.
If two lines have direction ratios (a<sub>1</sub>,b<sub>1</sub>,c<sub>1</sub>) and (a<sub>2</sub>,b<sub>2</sub>,c<sub>2</sub>), they are parallel if:
A a<sub>1</sub>a<sub>2</sub> + b<sub>1</sub>b<sub>2</sub> + c<sub>1</sub>c<sub>2</sub> = 0B a<sub>1</sub>/a<sub>2</sub> = b<sub>1</sub>/b<sub>2</sub> = c<sub>1</sub>/c<sub>2</sub>C a<sub>1</sub> = a<sub>2</sub>, b<sub>1</sub> = b<sub>2</sub>D a<sub>1</sub> + a<sub>2</sub> = 0Show answer & explanation →
Q13.
Direction ratios of the line joining A(1,2,3) and B(4,6,3) are:
A (1,2,3)B (3,4,0)C (4,6,3)D (5,8,6)Show answer & explanation →
Q14.
The distance from origin to the plane ax + by + cz = d is:
A dB d / (a+b+c)C |d| / sqrt(a<sup>2</sup>+b<sup>2</sup>+c<sup>2</sup>)D sqrt(a<sup>2</sup>+b<sup>2</sup>+c<sup>2</sup>)Show answer & explanation →
Q16.
The angle between two planes equals the angle between their:
A Normal vectorsB Tangent vectorsC Lines of intersectionD EdgesShow answer & explanation →
Q17.
A line is perpendicular to a plane if its direction is:
A Parallel to the planeB Along the normal to the planeC In the planeD At 45 degrees to the normalShow answer & explanation →
Q18.
The intercept form of a plane is x/a + y/b + z/c = 1. Here a, b, c are:
A Direction cosinesB x, y, z interceptsC SlopesD Coordinates of originShow answer & explanation →
Q19.
Three points A, B, C are collinear if the vectors AB and AC satisfy:
A AB . AC = 0, the dot product conditionB AB + AC = 0, a vector sum conditionC AB x AC = 0 (zero vector)D AB = BC, equal vector magnitudesShow answer & explanation →
Medium - 20 questions Q21.
Find the direction cosines of a line with direction ratios (2, -1, 2).
A (2/3, -1/3, 2/3)B (2, -1, 2)C (1/3, -1/3, 1/3)D (4/9, 1/9, 4/9)Show answer & explanation →
Q22.
The angle between lines with direction ratios (1,1,0) and (0,1,1) satisfies:
A cos(theta) = 0B cos(theta) = 1C cos(theta) = 1/2D cos(theta) = 1/sqrt(2)Show answer & explanation →
Q23.
Two lines are perpendicular if their direction ratios (a<sub>1</sub>,b<sub>1</sub>,c<sub>1</sub>) and (a<sub>2</sub>,b<sub>2</sub>,c<sub>2</sub>) satisfy:
A a<sub>1</sub>/a<sub>2</sub> = b<sub>1</sub>/b<sub>2</sub> = c<sub>1</sub>/c<sub>2</sub>B a<sub>1</sub>a<sub>2</sub> + b<sub>1</sub>b<sub>2</sub> + c<sub>1</sub>c<sub>2</sub> = 0C a<sub>1</sub>a<sub>2</sub> = b<sub>1</sub>b<sub>2</sub>D a<sub>1</sub>+a<sub>2</sub> = 0Show answer & explanation →
Q24.
The shortest distance between two parallel lines r = a + lambda*b and r = c + mu*b is:
A |(a-c) . b| / |b|B |(a-c) x b| / |b|C |a - c|D |(a-c) + b| / |b|Show answer & explanation →
Q25.
The equation of the plane through origin with normal vector (1, -2, 3) is:
A x - 2y + 3z = 0B x + 2y + 3z = 1C x - 2y + 3z = 1D 2x - y + 3z = 0Show answer & explanation →
Q27.
The shortest distance between skew lines r = a + lambda*b and r = c + mu*d is:
A |(a-c) . b|B |(c-a).(b x d)| / |b x d|C |(a-c) x (b+d)| / |b+d|D |(c-a) x d|Show answer & explanation →
Q28.
The angle between planes 2x+3y-z=5 and x-y+2z=3 satisfies cos(theta) =
A |-3| / (sqrt(14)*sqrt(6)), using only the absolute valueB 3 / (sqrt(14)*sqrt(6)), dropping the negative signC (2-3-2) / (sqrt(14)*sqrt(6)), an unsimplified numeratorD All three expressions are equivalentShow answer & explanation →
Q30.
The equation of a plane passing through three non-collinear points is found by:
A Averaging their coordinatesB Finding the normal using cross product of two edge vectorsC Using the dot product of edgesD Summing position vectorsShow answer & explanation →
Q31.
Two planes are parallel if their normal vectors are:
A Perpendicular to one another in directionB Proportional (parallel)C Equal in magnitude, regardless of directionD Pointing in exactly opposite directionsShow answer & explanation →
Q33.
The line through (1,2,3) perpendicular to plane 2x-y+3z=5 has direction ratios:
A (1,2,3)B (3,2,1)C (2,-1,3)D (1,-2,3)Show answer & explanation →
Q34.
Four points are coplanar if the vectors from one point to the other three satisfy:
A They are all equal in both magnitude and directionB Their vector sum adds up to exactly zeroC Their scalar triple product is zeroD They are all normalized to unit length vectorsShow answer & explanation →
Q35.
The foot of the perpendicular from the origin to the plane 3x+4y+5z=25 is:
A (3,4,5)B (1,2,3)C (3/5,4/5,1)D (1.5,2,2.5)Show answer & explanation →
Q37.
The line x/1 = y/2 = z/3 makes an angle with the y-axis such that:
A cos(beta) = 1/sqrt(14)B cos(beta) = 3/sqrt(14)C cos(beta) = 1/7D cos(beta) = 2/sqrt(14)Show answer & explanation →
Q38.
The line through A(2,1,3) and B(4,3,9) meets x+y+z=6 at the point:
A A itselfB B itselfC Midpoint of ABD (3,2,6)Show answer & explanation →
Hard - 28 questions Q41.
The shortest distance between skew lines x=y=z and (x+1)/1=y/2=z/3 is:
A 1/sqrt(6)B 1/sqrt(3)C 1/sqrt(2)D 0Show answer & explanation →
Q42.
The line through A(1,2,3) and B(4,5,6) meets the plane x+y+z=9 at:
A A itselfB (2,3,4)C (3,4,2)D B itselfShow answer & explanation →
Q43.
The equation of the plane containing line r = i + lambda*(2i+j-k) and parallel to i+j is:
A 2x-y-z=2B x-y+z=0C x-y+z=1D x+y+z=1Show answer & explanation →
Q46.
The plane through line of intersection of x+y+z=1 and 2x+3y+4z=5 and parallel to x-axis has equation:
A y + 2z = 3B x - y + z = 0C y - z = 1D x + y = 2Show answer & explanation →
Q47.
Two lines coplanar in space share a common plane. The normal to this plane is perpendicular to:
A Both line directionsB One line direction onlyC The line of intersectionD All vectors in spaceShow answer & explanation →
Q48.
The sphere centred at (1,-1,2) passing through the origin has equation:
A (x-1)<sup>2</sup>+(y+1)<sup>2</sup>+(z-2)<sup>2</sup>=6B x<sup>2</sup>+y<sup>2</sup>+z<sup>2</sup>=6C x<sup>2</sup>+y<sup>2</sup>+z<sup>2</sup>-2x+2y-4z=0D Both A and C are equivalentShow answer & explanation →
Q51.
The direction cosines of a line making equal angles with all coordinate axes are:
A (1,1,1), an unnormalized direction vectorB (1/sqrt(2),1/sqrt(2),0), normalized in only two axesC (1/3,1/3,1/3), a vector that is not properly normalizedD (1/sqrt(3),1/sqrt(3),1/sqrt(3))Show answer & explanation →
Q53.
Two planes x+2y+3z=4 and 2x+4y+6z=5 are:
A Intersecting perpendicular planesB Coincident planesC Parallel planes (not the same)D Perpendicular planesShow answer & explanation →
Q54.
If a line makes angles alpha, beta, gamma with x, y, z axes respectively, then sin<sup>2</sup>(alpha)+sin<sup>2</sup>(beta)+sin<sup>2</sup>(gamma) =
Show answer & explanation →
Q55.
The angle bisector planes of two intersecting planes bisect the:
A The normal vectors of each individual planeB Dihedral angle between the planesC The lines of intersection between the planesD The direction cosines of the planes' normalsShow answer & explanation →
Q56.
The shortest distance between the lines x=1,y=2 and y=3,z=4 (lines parallel to z-axis and x-axis respectively) is:
A sqrt(2)B sqrt(5)C sqrt(10)D 1Show answer & explanation →
Q57.
The plane passing through (0,0,0), (1,0,0) and (0,1,1) has normal:
A (0,1,-1)B (1,1,0)C (0,-1,1)D (1,-1,0)Show answer & explanation →
Q58.
The equation of the plane passing through (1,0,-1), (3,2,2), (-1,-1,-2) and passing through all three is:
A x-4y+2z=-1B x-4y+2z=1C x+4y-2z=1D 2x-3y+z=2Show answer & explanation →
Q63.
The direction cosines of a line equally inclined to the three coordinate axes are:
A 1/3 eachB 1/√3 eachC 1/√2 eachD 1 eachShow answer & explanation →
Q64.
The foot of the perpendicular from the origin to the plane 2x + 3y + 6z = 49 is:
A (2, 3, 6)B (1, 1.5, 3)C (4, 6, 12)D (2, 3, 7)Show answer & explanation →
Q65.
The equation of the plane through (1,0,0), (0,1,0) and (0,0,1) is:
A x + y + z = 1B x + y + z = 0C x + y + z = 3D xyz = 1Show answer & explanation →
Q66.
The line with direction (1, 2, 2) and the plane 2x − 2y + z = 5 are:
A parallel to each otherB perpendicularC inclined at 30°D inclined at 45°Show answer & explanation →
Q68.
The lines (x−1)/2 = (y−2)/3 = (z−3)/4 and (x−2)/3 = (y−3)/4 = (z−4)/5 are:
A skewB coplanarC parallelD perpendicularShow answer & explanation →