Medians and Centroid of a Triangle

Table Of Contents

🎬 Math Angel Video: Medians and Centroid Explained

What is Median of a Triangle?

The definition of a median of a triangle is that it connects a vertex to the midpoint of the opposite side, dividing it into two equal-area triangles.

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🛎 Definition of a Median:

A median of a triangle is a line segment that connects a vertex to the midpoint of the opposite side.

🛎 A Key Property of a Median:

A median divides the triangle into two smaller triangles of equal area, no matter what the triangle looks like.

What is Centroid of a Triangle?

The definition of the centroid of a triangle is the point where the three medians intersect, dividing each median in a 2:1 ratio.

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🛎 Definition of a Centroid:

The centroid of a triangle is the point where all three medians intersect.


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A Key Property of a Centroid:

The centroid has a special property: It divides each median into two segments in a ratio of 2:1.

That means the part of the median from the vertex to the centroid is twice as long as the part from the centroid to the midpoint of the side

Practice: Median and Centroid of a Triangle

The median and centroid of a triangle apply to the problem.

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Point D is the centroid of triangle ABC. Points E, F, G are the midpoints of the sides.

We are given:

  • $AE = 5$
  • $AD = 6$
  • $DE = 4$

Now let’s find some missing lengths:

1. Find $AB$
Since $E$ is the midpoint of $AB$,
$AB = 2 \times AE = 2 \times 5 = 10$

2. Find $DG$
Since $D$ is the centroid, it divides each median in a $2:1$ ratio.
So $DG = \tfrac{1}{2} \times AD = \tfrac{1}{2} \times 6 = 3$

3. Find $CE$
$CE = CD + DE$
Since $D$ is the centroid, $CD = 2 \times DE = 2 \times 4 = 8$
So $CE = 8 + 4 = 12$

🍪 Quiz: Practice Medians and Centroid of Triangles

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Medians and Centroid of a Triangle

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Q: AD is a median of triangle ABC. If BD = 5 cm, what is the length of CD?

Triangle ABC with median AD, point D on base BC dividing it into 5?cm and unknown length marked with a question mark.

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Q: What is the name of the point where the medians of a triangle intersect?

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Q: If AD is a median and E is the centroid of triangle ABC, and AE = 6 cm, what is the length of ED?

Triangle ABC with median AD, point E on AD marked 6 cm from A, unknown distance from D to E shown with a question mark.

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Q: If CG is a median and E is the centroid of triangle ABC, and the area of triangle AGC is 10 cm², what is the area of triangle ABC?

Triangle ABC with shaded triangle AGC, area 10 cm², and point E marked on median GC.

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Q: If BF is a median and E is the centroid of triangle ABC, and BF = 12 cm, what is the length of BE?

 

Triangle ABC with median BF, point E on BF and BF = 12 cm, unknown length from E to F shown with a question mark.

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Q: If E is the centroid of triangle ABC, and you know that AE= 10 cm, what is the length of the median AD?

Triangle ABC with medians intersecting at E, AE marked 10 cm with unknown length from E to midpoint of BC shown in pink.

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