A triangle has corners at #(9 ,1 )#, #(6 ,7 )#, and #(3 ,2 )#. How far is the triangle's centroid from the origin?

1 Answer
Apr 23, 2018

#" "#
The triangle's Centroid is #color(red)("6.3 Units"# away from the Origin.

Explanation:

#" "#
#color(green)("Step 1"#

Construct a triangle ABC with Vertices as given:

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#color(green)("Step 2"#

A Centroid of a triangle ABC is the point where the three medians of the triangle meet.

A median of a triangle is a line segment from one vertex to the mid point on the opposite side of the triangle.

Mark the Mid-Points of the line segments #AB, BC and AC#.

Call these mid-points #D, E and F#.

Mid-Point of Side #bar (AB)# is #color(blue)(D.#

Mid-Point of Side #bar(BC)# is #color(blue)(E.#

Mid-Point of Side #bar(AC)# is #color(blue)(F.#

Join Side #bar (AB)# to the #color(red)("Vertex C".#

Join Side #bar (BC)# to the #color(red)("Vertex A".#

Join Side #bar (AC)# to the #color(red)("Vertex B".#

enter image source here

You can see that the all the three Medians intersect at a point.

This point is called the Centroid.

#color(green)("Step 3"#

Identify the Origin (O) with coordinates #(0,0)#.

Mark the Centroid and name it as Centroid.

Connect the Origin and the Centroid.

enter image source here

Measure the length of the line segment joining the Origin and the Centroid.

The magnitude #~~ " 6.227 Units"#.

Hence, the required answer.

You can write your final solution as:

The triangle's Centroid is #color(red)("6.3 Units"# away from the Origin.

An interesting observation to note:

The three line segments #bar(AB), bar(BC) and bar(AC)# intersect at one point if and only if:

#color(blue)(bar(AD)/bar(BD) = 1#

#color(blue)(bar(BE)/bar(CE) = 1#

#color(blue)(bar(CF)/bar(AF) = 1#

This property is known as Ceva's Theorem.

Hope it helps.