How many in this one:

]]>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.