Triangle Median Problem: Calculate BC Length Given AD as Median

Triangle Medians with Midpoint Properties

AD is the median.

Calculate the length of the side BC.

AAABBBCCCDDD6

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Calculate side BC
00:03 The entire side equals the sum of its parts
00:09 AD is a median according to the given data, the median bisects the side
00:17 Place BD instead of DC (they are equal because AD is a median)
00:28 Substitute the value of BD according to the given data and solve for BC
00:31 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

AD is the median.

Calculate the length of the side BC.

AAABBBCCCDDD6

2

Step-by-step solution

Given that AD AD is a median in triangle ABC \triangle ABC and BD=6 BD = 6 , we need to determine the length of side BC BC .

Since AD AD is the median, it implies that D D is the midpoint of BC BC . By definition of midpoint, this means:

  • BD=DC BD = DC .
  • Given BD=6 BD = 6 , it follows that DC=6 DC = 6 as well, since D D divides BC BC into two equal parts.

Therefore, the total length of BC BC can be calculated as:

BC=BD+DC=6+6=12 BC = BD + DC = 6 + 6 = 12 .

Thus, the length of side BC BC is 12.

3

Final Answer

12

Key Points to Remember

Essential concepts to master this topic
  • Definition: A median connects vertex to midpoint of opposite side
  • Technique: Since D D is midpoint, BD=DC=6 BD = DC = 6
  • Check: Verify midpoint divides side equally: BC=6+6=12 BC = 6 + 6 = 12

Common Mistakes

Avoid these frequent errors
  • Using median length instead of side segment
    Don't confuse the median AD AD with side segment BD=6 BD = 6 ! Students often try to use the median length as the full side length. Always remember that the median goes from vertex to midpoint, while we need the full side which equals two equal segments.

Practice Quiz

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Is the straight line in the figure the height of the triangle?

FAQ

Everything you need to know about this question

What exactly is a median in a triangle?

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A median is a line segment that connects any vertex of a triangle to the midpoint of the opposite side. Every triangle has exactly 3 medians!

How do I know D is the midpoint of BC?

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The problem states that AD is the median. By definition, this means A connects to the midpoint of the opposite side BC, so D must be that midpoint.

Why are BD and DC equal?

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Since D is the midpoint of BC, it divides BC into two equal parts. This is what "midpoint" means - the point that splits a line segment exactly in half.

What if BD was a different number?

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The method stays the same! If BD=8 BD = 8 , then DC=8 DC = 8 too, so BC=8+8=16 BC = 8 + 8 = 16 . The key is that both segments are always equal.

Can I solve this without knowing about medians?

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Not really! Understanding that medians create midpoints is essential. Without this concept, you wouldn't know that D divides BC into two equal parts.

Do all triangles have the same median properties?

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Yes! Every triangle - whether scalene, isosceles, or equilateral - has medians that connect vertices to midpoints. This property never changes.

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