Math Is Fun Forum

kuba.g

Member

Registered: 2005-10-10

Posts: 1

Count the triangles inside a triangle

Hi,

Our maths teacher gave us this puzzle:

He first showed us the triagle above and asked how many triangles are in it.
Everyone said 9.
But he said it there ware 35, and he asked if we can find the formula for it.

He also showed this:

This one is ment to be 25 triangles???

Does anyone know the formula for it?
Please don't use too complicated terms as I'm only 13
It would be nice if I'm the only one of the class to know the answer.

Thanks a lot in advance,
Kuba.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Count the triangles inside a triangle

I can only find 9 in the first one and 8 in the second one. Maybe one of the other members can offer some dramatic revelation that makes the rest if us look stupid, but if not then your teacher's probably just made a mistake.

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Why did the vector cross the road?
It wanted to be normal.

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,711

Re: Count the triangles inside a triangle

Likewise I get 9 for the first and 8 for the second. Maybe you were supposed to add some lines?

How many in this one:

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman