BoardMaths

Three Dimensional Geometry

25 Board Maths previous year questions on Three Dimensional Geometry — options free on every question; 2 include the answer & explanation free, the rest unlock with PYQ Pass.

Q1 FREE PREVIEW
PYQ

Direction ratios of a vector parallel to line \(\frac{x-1}{2}=-y=\frac{2 z+1}{6}\) are :

a

\(2,-1,6\)

b

\(2,1,6\)

c

\(2,1,3\)

d

\(2,-1,3\)

✓ Correct answer: d)

\(2,-1,3\)

Explanation

Given equation of the line is

\( \frac{x-1}{2}=-y=\frac{2 z+1}{6} \)
\( \Rightarrow \frac{x-1}{2}=\frac{y-0}{-1}=\frac{2\left(z+\frac{1}{2}\right)}{6} \)
\( \Rightarrow \frac{x-1}{2}=\frac{y-0}{-1}=\frac{z+\frac{1}{2}}{3}\)

The direction ratios of the line are \((2,-1,3)\).

Q2 FREE PREVIEW
PYQ

Direction ratios of a vector parallel to line \(\frac{x-1}{2}=-y=\frac{2 z+1}{6}\) are :

a

\(2,-1,6\)

b

\(2,1,6\)

c

\(2,1,3\)

d

\(2,-1,3\)

✓ Correct answer: d)

\(2,-1,3\)

Explanation

Let \(\frac{x-1}{2}=-y=\frac{2 z+1}{6}=\lambda\)

\(x=1+2 \lambda \Rightarrow \frac{d x}{d \lambda}=2\)

\(-y=\lambda \Rightarrow y=-\lambda\)

\(\Rightarrow \frac{d y}{d \lambda}=-1\)

\(\frac{2 z+1}{6}=\lambda \Rightarrow 2 z=6 \lambda-1\)

\(\Rightarrow z=3 \lambda-\frac{1}{2} \Rightarrow \frac{d z}{d \lambda}=3\)

Q3
PYQ

Assertion (A) : A line in space cannot be drawn perpendicular to \(\mathrm{x}, \mathrm{y}\) and \(z\) axes simultaneously.

Reason \((R)\) : For any line making angles, \(\alpha, \beta, \gamma\) with the positive directions of \(x, y\) and \(z\) axes respectively, then \(\cos ^2 \alpha+\cos ^2 \beta+\cos ^2 \gamma=1\).

a

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

b

Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

c

Assertion (A) is true, but Reason (R) is false.

d

Assertion (A) is false, but Reason (R) is true.

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Q4
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The equation of a line parallel to the vector \(3\hat{i}+\hat{j}+2\hat{k}\) and passing through the point \((4,-3,7)\) is :

a

\(x=4\mathrm{t}+3,\mathrm{y}=-3\mathrm{t}+1,\mathrm{z}=7\mathrm{t}+2\)

b

\(x=3\mathrm{t}+4,\mathrm{y}=\mathrm{t}+3,\mathrm{z}=2\mathrm{t}+7\)

c

\(x=3\mathrm{t}+4,\mathrm{y}=\mathrm{t}-3,\mathrm{z}=2\mathrm{t}+7\)

d

\(x=3t+4,y=-t+3,z=2t+7\)

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Q5
PYQ

The distance of point \(\mathrm{P}(\mathrm{a}, \mathrm{b}, \mathrm{c})\) from y -axis is :

a

\(\mathrm{b}\)

b

\(\mathrm{b}^2\)

c

\(\sqrt{\mathrm{a}^2+\mathrm{c}^2}\)

d

\(\mathrm{a}^2+\mathrm{c}^2\)

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Q6
PYQ

The distance of point \(\mathrm{P}(\mathrm{a}, \mathrm{b}, \mathrm{c})\) from y -axis is :

a

\(\mathrm{b}\)

b

\(\mathrm{b}^2\)

c

\(\sqrt{\mathrm{a}^2+\mathrm{c}^2}\)

d

\(\mathrm{a}^2+\mathrm{c}^2\)

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Q7
PYQ

The coordinates of the foot of the perpendicular drawn from the point \((0,1,2)\) on the \(x\)-axis are given by :

a

\((1,0,0)\)

b

\((2,0,0)\)

c

\((\sqrt{5}, 0,0)\)

d

\((0,0,0)\)

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Q8
PYQ

If a line makes an angle of \(30^{\circ}\) with the positive direction of \(x\)-axis, \(120^{\circ}\) with the positive direction of \(y\)-axis, then the angle which it makes with the positive direction of \(z\)-axis is :

a

\(90^{\circ}\)

b

\(120^{\circ}\)

c

\(60^{\circ}\)

d

\(0^{\circ}\)

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Q9
PYQ

The angle which the line \(\frac{x}{1}=\frac{\mathrm{y}}{-1}=\frac{\mathrm{z}}{0}\) makes with the positive direction of Y -axis is :

a

\(\frac{5\pi }{6}\)

b

\(\frac{3\pi }{4}\)

c

\(\frac{5\pi }{4}\)

d

\(\frac{7\pi }{4}\)

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Q10
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The line \(x=1+5\mu ,y=-5+\mu ,z=-6-3\mu\) passes through which of the following point?

a

\((1,-5,6)\)

b

\((1,5,6)\)

c

\((1,-5,-6)\)

d

\((-1,-5,6)\)

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Q11
PYQ

The equation of a line parallel to the vector \(3\hat{i}+\hat{j}+2\hat{k}\) and passing through the point \((4,-3,7)\) is :

a

\(x=4\mathrm{t}+3,\mathrm{y}=-3\mathrm{t}+1,\mathrm{z}=7\mathrm{t}+2\)

b

\(x=3\mathrm{t}+4,\mathrm{y}=\mathrm{t}+3,\mathrm{z}=2\mathrm{t}+7\)

c

\(x=3\mathrm{t}+4,\mathrm{y}=\mathrm{t}-3,\mathrm{z}=2\mathrm{t}+7\)

d

\(x=3t+4,y=-t+3,z=2t+7\)

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Q12
PYQ

If a line makes an angle of \(30^{\circ}\) with the positive direction of \(x\)-axis, \(120^{\circ}\) with the positive direction of \(y\)-axis, then the angle which it makes with the positive direction of \(z\)-axis is :

a

\(90^{\circ}\)

b

\(120^{\circ}\)

c

\(60^{\circ}\)

d

\(0^{\circ}\)

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Q13
PYQ

The Cartesian equation of the line passing through the point \(\left(1,-3,2\right)\) and parallel to the line : \(\vec{\mathrm{r}}=\left(2+\lambda \right)\hat{\mathrm{i}}+\lambda \hat{\mathrm{j}}+\left(2\lambda -1\right)\hat{\mathrm{k}}\) is

a

\(\frac{\mathrm{x}-1}{2}=\frac{\mathrm{y}+3}{0}=\frac{\mathrm{z}-2}{-1}\)

b

\(\frac{\mathrm{x}+1}{1}=\frac{\mathrm{y}-3}{1}=\frac{\mathrm{z}+2}{2}\)

c

\(\frac{\mathrm{x}+1}{2}=\frac{\mathrm{y}-3}{0}=\frac{\mathrm{z}+2}{-1}\)

d

\(\frac{\mathrm{x}-1}{1}=\frac{\mathrm{y}+3}{1}=\frac{\mathrm{z}-2}{2}\)

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Q14
PYQ

The Cartesian equation of the line passing through the point \((1,-3,2)\) and parallel to the line : \(\vec{\mathrm{r}}=(2+\lambda )\hat{\mathrm{i}}+\lambda \hat{\mathrm{j}}+(2\lambda -1)\hat{\mathrm{k}}\) is

a

\(\frac{\mathrm{x}-1}{2}=\frac{\mathrm{y}+3}{0}=\frac{\mathrm{z}-2}{-1}\)

b

\(\frac{\mathrm{x}+1}{1}=\frac{\mathrm{y}-3}{1}=\frac{\mathrm{z}+2}{2}\)

c

\(\frac{\mathrm{x}+1}{2}=\frac{\mathrm{y}-3}{0}=\frac{\mathrm{z}+2}{-1}\)

d

\(\frac{\mathrm{x}-1}{1}=\frac{\mathrm{y}+3}{1}=\frac{\mathrm{z}-2}{2}\)

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Q15
PYQ

The angle which the line \(\frac{x}{1}=\frac{\mathrm{y}}{-1}=\frac{\mathrm{z}}{0}\) makes with the positive direction of Y -axis is :

a

\(\frac{5\pi }{6}\)

b

\(\frac{3\pi }{4}\)

c

\(\frac{5\pi }{4}\)

d

\(\frac{7\pi }{4}\)

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Q16
PYQ

If the direction cosines of a line are \(\sqrt{3} \mathrm{k}, \sqrt{3} \mathrm{k}, \sqrt{3} \mathrm{k}\), then the value of k is :

a

\(\pm 1\)

b

\(\pm \sqrt{3}\)

c

\(\pm 3\)

d

\(\pm \frac{1}{3}\)

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Q17
PYQ

If a line makes angles of \(\frac{3\pi }{4},\frac{\pi }{3}\) and \(\theta\) with the positive directions of \(x, y\) and \(z\)-axis respectively, then \(\theta\) is

a

\(\frac{-\pi}{3}\) only

b

\(\frac{\pi}{3}\) only

c

\(\frac{\pi }{6}\)

d

\(\pm \frac{\pi }{3}\)

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Q18
PYQ

If the direction cosines of a line are \(\sqrt{3} \mathrm{k}, \sqrt{3} \mathrm{k}, \sqrt{3} \mathrm{k}\), then the value of k is :

a

\(\pm 1\)

b

\(\pm \sqrt{3}\)

c

\(\pm 3\)

d

\(\pm \frac{1}{3}\)

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Q19
PYQ

The coordinates of the foot of the perpendicular drawn from the point \((0,1,2)\) on the \(x\)-axis are given by :

a

\((1,0,0)\)

b

\((2,0,0)\)

c

\((\sqrt{5}, 0,0)\)

d

\((0,0,0)\)

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Q20
PYQ

The line \(x=1+5\mu ,y=-5+\mu ,z=-6-3\mu\) passes through which of the following point?

a

\((1,-5,6)\)

b

\((1,5,6)\)

c

\((1,-5,-6)\)

d

\((-1,-5,6)\)

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Q21
PYQ

If a line makes angles of \(\frac{3\pi }{4},\frac{\pi }{3}\) and \(\theta\) with the positive directions of \(x, y\) and \(z\)-axis respectively, then \(\theta\) is

a

\(\frac{-\pi}{3}\) only

b

\(\frac{\pi}{3}\) only

c

\(\frac{\pi }{6}\)

d

\(\pm \frac{\pi }{3}\)

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Q22
PYQ

Assertion (A) : A line in space cannot be drawn perpendicular to \(\mathrm{x}, \mathrm{y}\) and z axes simultaneously.

Reason \((R)\) : For any line making angles, \(\alpha, \beta, \gamma\) with the positive directions of \(x, y\) and \(z\) axes respectively, \(\cos ^2 \alpha+\cos ^2 \beta+\cos ^2 \gamma=1\).

a

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

b

Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

c

Assertion (A) is true, but Reason (R) is false.

d

Assertion (A) is false, but Reason (R) is true.

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Q23
PYQ

The shortest distance between the lines \(\frac{\mathrm{x}-3}{2}=\frac{\mathrm{y}-2}{3}=\frac{\mathrm{z}-1}{-1}\) and \(\frac{\mathrm{x}+3}{2}=\frac{\mathrm{y}-6}{1}=\frac{\mathrm{z}-5}{3}\) is :

a

\(\frac{18}{\sqrt{5}}\)

b

\(\frac{22}{3 \sqrt{5}}\)

c

\(\frac{46}{3 \sqrt{5}}\)

d

\(6 \sqrt{3}\)

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Q24
PYQ

The shortest distance between the lines \(\frac{x+2}{1}=\frac{y}{-2}=\frac{z-5}{2}\) and \(\frac{x-4}{1}=\frac{y-1}{2}=\frac{z+3}{0}\) is

[JEE Main 2023, 10 Apr (Shift 1)]

a

6

b

9

c

7

d

8

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Q25
PYQ

The equation of the plane with intercepts of 2,3 and 4 on the x, y and z-axes respectively is -

a

4x+6y+3z=12

b

6x+4y+3z=12

c

3x+4y+6z=12

d

\(5x+4y+3z=0\)

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