Median AD = 18, find GD

Step by step

The question

Question: A D is a median of triangle A B C and G is where the medians meet, with AD = 18: find GD.

1 Use the median rule

A median goes from a corner to the middle of the opposite side.

D is the middle of B C.

The three medians all meet at one point, G.

It is called the centroid.

G cuts each median into 2 parts and 1 part: the long part from the corner.

2 Find one part

A D is 3 equal parts: 2 for A G and 1 for G D.

18 divided by 3 is 6.

Careful!

G is not the middle of the median.

A G is 2 parts out of 3.

3 Find GD

GD is 1 part: 6.

4 Check

Let's check: A G plus G D is 18, the whole median.

And A G is twice G D.

So it is right!

Let's look back.

First: use the median rule.

Then: find one part.

Then: find GD.

Last: check.