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Question: Answered & Verified by Expert
Let PQR be a triangle with R(-1,4,2). Suppose M(2,1,2) is the mid point of PQ. The distance of the centroid of PQR from the point of intersection of the line x-20=y2=z+3-1 and x-11=y+3-3=z+11 is
MathematicsThree Dimensional GeometryJEE MainJEE Main 2024 (29 Jan Shift 1)
Options:
  • A 69
  • B 9
  • C 69
  • D 99
Solution:
1952 Upvotes Verified Answer
The correct answer is: 69

Given: 

x-20=y2=z+3-1 and x-11=y+3-3=z+11

x-20=y2=z+3-1=klet

x=2, y=2k, z=-k+3   ...i

Also, x-11=y+3-3=z+11=λlet

x=λ+1, y=-3λ-3. z=λ-1   ...ii

Using i and ii,

2=λ+1, 2k=-3λ-3

λ=1, 2k=-3-3

λ=1, k=-3

x=2, y=-6, z=0

So, the intersection point of two given lines is 2,-6,0.

Now, we know that centroid G divides MR (median) in the ratio 1 : 2.

So, by using section formula, G1×-1+2×23,1×4+2×13,1×2+2×23

So, centroid is G(1, 2, 2).

Let A be the point of intersection of given lines.

AG=2-12+2+62+2-02

AG=1+64+4

AG=69

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