Centroid segment length – Triangle XYZ with sides 11, 14, 7 cm:\nG is centroid and M is the midpoint of XY. Given XY = 11 cm, YZ = 14 cm, XZ = 7 cm. Find GM (in cm).

Difficulty: Hard

Correct Answer: 3

Explanation:


Introduction / Context:
The centroid divides each median in the ratio 2:1 from vertex to midpoint. Thus, GM equals one-third of the median length from the opposite vertex to side XY.


Given Data / Assumptions:

  • Let median from Z meet XY at M (midpoint of XY).
  • Sides: XY = 11, XZ = 7, YZ = 14.


Concept / Approach:
Median to side a (opposite vertex) has length m = (1/2) * √(2b^2 + 2c^2 − a^2). Here a = XY, b = XZ, c = YZ. Then GM = (1/3) * m.


Step-by-Step Solution:

m_Z = (1/2) * √(2*7^2 + 2*14^2 − 11^2) = (1/2)*√(98 + 392 − 121) = (1/2)*√369.√369 ≈ 19.235 ⇒ m_Z ≈ 9.6175.GM = (1/3)*m_Z ≈ 3.2058 ≈ 3 cm (to nearest whole cm).


Verification / Alternative check:
Using exact radical form confirms GM ≈ 3.206 cm; the nearest provided value is 3.


Common Pitfalls:
Using 2/3 instead of 1/3 for the segment from centroid to midpoint; mixing the side labels in the median formula.


Final Answer:
3

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